diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..3546131c8 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,7 +1,11 @@
 // Predict and explain first...
 
+//answer:  this code defines an object called address, and it has several properties (key–value pairs).
+
 // This code should log out the houseNumber from the address object
 // but it isn't working...
+//answer : it doesnt work because in object,  we dont use numeric index and the result is undefined
+
 // Fix anything that isn't working
 
 const address = {
@@ -12,4 +16,5 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+// console.log(`My house number is ${address[0]}`); wrong
+console.log(`My house number is ${address.houseNumber}`); //correct
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..746ba6894 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -3,6 +3,8 @@
 // This program attempts to log out all the property values in the object.
 // But it isn't working. Explain why first and then fix the problem
 
+//answer : the result is TypeError: author is not iterable  Because objects are not iterable with for...of — that loop only works with arrays, strings, and other iterable types.
+
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +13,10 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+// for (const value of author) {    wrong code
+//   console.log(value);
+// }
+
+for (const value of Object.values(author)) {
   console.log(value);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..5a255b392 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -4,12 +4,24 @@
 // Each ingredient should be logged on a new line
 // How can you fix it?
 
+//answer :
+// ${recipe.title} → "bruschetta"
+
+// ${recipe.serves} → 2
+
+// ${recipe} → wrong!  = > because recipe is an object, and when you interpolate it into a string, it becomes:
+
+// [object Object]
+
 const recipe = {
   title: "bruschetta",
   serves: 2,
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+console.log(recipe.title + "serves" + recipe.serves);
+console.log("ingredients:");
+
+for (let i = 0; i < recipe.ingredients.length; i++) {
+  console.log(recipe.ingredients[i]);
+}
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..4bb1ebb46 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,13 @@
-function contains() {}
+// Implement the contains function
+function contains(obj, propName) {
+  // Check that the first argument is an object, not null or an array
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    return false;
+  }
 
+  // Check if the object has the property
+  return obj.hasOwnProperty(propName);
+}
+
+// Export the function so other files can use it
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..0e756f880 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -3,33 +3,31 @@ const contains = require("./contains.js");
 /*
 Implement a function called contains that checks an object contains a
 particular property
-
-E.g. contains({a: 1, b: 2}, 'a') // returns true
-as the object contains a key of 'a'
-
-E.g. contains({a: 1, b: 2}, 'c') // returns false
-as the object doesn't contains a key of 'c'
 */
 
-// Acceptance criteria:
-
-// Given a contains function
-// When passed an object and a property name
-// Then it should return true if the object contains the property, false otherwise
-
-// Given an empty object
-// When passed to contains
-// Then it should return false
-test.todo("contains on empty object returns false");
-
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
-
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
-
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error
+// Test 1: Empty object
+test("contains on empty object returns false", () => {
+  expect(contains({}, "a")).toBe(false);
+});
+
+// Test 2: Existing property
+test("returns true when the property exists in the object", () => {
+  const obj = { a: 1, b: 2 };
+  expect(contains(obj, "a")).toBe(true);
+});
+
+// Test 3: Non-existent property
+test("returns false when the property does not exist in the object", () => {
+  const obj = { a: 1, b: 2 };
+  expect(contains(obj, "c")).toBe(false);
+});
+
+// Test 4: Invalid input - array
+test("returns false if input is an array", () => {
+  expect(contains([], "a")).toBe(false);
+});
+
+// Test 5: Invalid input - null
+test("returns false if input is null", () => {
+  expect(contains(null, "a")).toBe(false);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..76aedea36 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,22 @@
-function createLookup() {
-  // implementation here
+// This function takes an array of country-currency pairs
+// and turns it into an object where keys are country codes
+// and values are currency codes
+function createLookup(pairs) {
+  // Create an empty object to store the result
+  const lookup = {};
+
+  // Loop through each pair in the array
+  for (let i = 0; i < pairs.length; i++) {
+    const pair = pairs[i]; // e.g. ['US', 'USD']
+    const country = pair[0]; // first element is country code
+    const currency = pair[1]; // second element is currency code
+
+    lookup[country] = currency; // add it to the object
+  }
+
+  // Return the final lookup object
+  return lookup;
 }
 
+// Export the function so it can be used in tests or other files
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..54e0c8c64 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,35 +1,45 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
-
 /*
-
-Create a lookup object of key value pairs from an array of code pairs
-
-Acceptance Criteria:
-
-Given
- - An array of arrays representing country code and currency code pairs
-   e.g. [['US', 'USD'], ['CA', 'CAD']]
-
-When
- - createLookup function is called with the country-currency array as an argument
-
-Then
- - It should return an object where:
- - The keys are the country codes
- - The values are the corresponding currency codes
-
-Example
-Given: [['US', 'USD'], ['CA', 'CAD']]
-
-When
-createLookup(countryCurrencyPairs) is called
-
-Then
-It should return:
- {
-   'US': 'USD',
-   'CA': 'CAD'
- }
+Implement a function called createLookup that turns an array of
+country-currency code pairs into an object.
 */
+
+// Test 1: multiple pairs
+test("creates a country currency code lookup for multiple codes", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+    ["GB", "GBP"],
+  ];
+  const expected = {
+    US: "USD",
+    CA: "CAD",
+    GB: "GBP",
+  };
+  expect(createLookup(input)).toEqual(expected);
+});
+
+// Test 2: empty array should return empty object
+test("returns empty object when given an empty array", () => {
+  const input = [];
+  const expected = {};
+  expect(createLookup(input)).toEqual(expected);
+});
+
+// Test 3: single pair
+test("works with a single country-currency pair", () => {
+  const input = [["JP", "JPY"]];
+  const expected = { JP: "JPY" };
+  expect(createLookup(input)).toEqual(expected);
+});
+
+// Test 4: duplicate keys (last one wins)
+test("handles duplicate country codes (last value wins)", () => {
+  const input = [
+    ["US", "USD"],
+    ["US", "USN"],
+  ];
+  const expected = { US: "USN" }; // last one overwrites
+  expect(createLookup(input)).toEqual(expected);
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..73f81e400 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,13 +1,24 @@
 function parseQueryString(queryString) {
   const queryParams = {};
-  if (queryString.length === 0) {
+
+  // Return empty object if input is empty
+  if (!queryString || queryString.length === 0) {
     return queryParams;
   }
+
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    // Split only on the first '='
+    const index = pair.indexOf("=");
+    if (index === -1) {
+      // No '=' in this pair, treat as key with empty string value
+      queryParams[pair] = "";
+    } else {
+      const key = pair.slice(0, index);
+      const value = pair.slice(index + 1);
+      queryParams[key] = value;
+    }
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..bb486cc76 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -1,12 +1,31 @@
-// In the prep, we implemented a function to parse query strings.
-// Unfortunately, it contains several bugs!
-// Below is one test case for an edge case the implementation doesn't handle well.
-// Fix the implementation for this test, and try to think of as many other edge cases as possible - write tests and fix those too.
+const parseQueryString = require("./querystring.js");
 
-const parseQueryString = require("./querystring.js")
+// Test 1: normal key=value pairs
+test("parses simple query string", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({ a: "1", b: "2" });
+});
 
+// Test 2: value contains '='
 test("parses querystring values containing =", () => {
-  expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
-  });
+  expect(parseQueryString("equation=x=y+1")).toEqual({ equation: "x=y+1" });
+});
+
+// Test 3: empty string returns empty object
+test("returns empty object for empty query string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+// Test 4: key without value
+test("parses key without value as empty string", () => {
+  expect(parseQueryString("keyWithoutValue")).toEqual({ keyWithoutValue: "" });
+});
+
+// Test 5: multiple keys including empty value
+test("parses multiple keys including empty values", () => {
+  expect(parseQueryString("a=1&b=&c=3")).toEqual({ a: "1", b: "", c: "3" });
+});
+
+// Test 6: only & characters with empty keys
+test("handles consecutive & correctly", () => {
+  expect(parseQueryString("a=1&&b=2")).toEqual({ a: "1", b: "2", "": "" });
 });
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..5601bdda3 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,23 @@
-function tally() {}
+function tally(items) {
+  // Check if input is an array
+  if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  const result = {};
+
+  // Loop through each item in the array
+  for (const item of items) {
+    // If the item already exists in result, increment the count
+    if (result[item]) {
+      result[item] += 1;
+    } else {
+      // Otherwise, initialize the count to 1
+      result[item] = 1;
+    }
+  }
+
+  return result;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..87ee7d556 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -1,34 +1,26 @@
 const tally = require("./tally.js");
 
-/**
- * tally array
- *
- * In this task, you'll need to implement a function called tally
- * that will take a list of items and count the frequency of each item
- * in an array
- *
- * For example:
- *
- * tally(['a']), target output: { a: 1 }
- * tally(['a', 'a', 'a']), target output: { a: 3 }
- * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
- */
+// Test 1: empty array should return empty object
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
 
-// Acceptance criteria:
+// Test 2: array with single item
+test("counts a single item", () => {
+  expect(tally(["a"])).toEqual({ a: 1 });
+});
 
-// Given a function called tally
-// When passed an array of items
-// Then it should return an object containing the count for each unique item
+// Test 3: array with multiple duplicates
+test("counts duplicates correctly", () => {
+  expect(tally(["a", "a", "a"])).toEqual({ a: 3 });
+});
 
-// Given an empty array
-// When passed to tally
-// Then it should return an empty object
-test.todo("tally on an empty array returns an empty object");
+// Test 4: array with multiple unique items
+test("counts multiple unique items correctly", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+});
 
-// Given an array with duplicate items
-// When passed to tally
-// Then it should return counts for each unique item
-
-// Given an invalid input like a string
-// When passed to tally
-// Then it should throw an error
+// Test 5: invalid input should throw an error
+test("throws an error if input is not an array", () => {
+  expect(() => tally("not an array")).toThrow("Input must be an array");
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..ed25ee36e 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -18,12 +18,24 @@ function invert(obj) {
 
 // a) What is the current return value when invert is called with { a : 1 }
 
+// // returns { key: 1 } : Wrong because invertedObj.key = value; literally uses the string "key" as a property instead of using the variable key
+
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
 
+//// returns { key: 2 }  Only one property "key" exists. It overwrites "key" twice.
+
 // c) What is the target return value when invert is called with {a : 1, b: 2}
 
+//{ "1": "a", "2": "b" }
+
 // c) What does Object.entries return? Why is it needed in this program?
 
+//Object.entries(obj) returns an array of key-value pairs. Needed because we want to loop over each key-value pair in the object.
+
 // d) Explain why the current return value is different from the target output
 
+//invertedObj.key = value; → sets the literal property "key" instead of using the variable value as the
+
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+//
diff --git a/Sprint-3/package.json b/Sprint-3/package.json
index 711a5390f..c58a56a6b 100644
--- a/Sprint-3/package.json
+++ b/Sprint-3/package.json
@@ -26,7 +26,7 @@
     "@testing-library/dom": "^10.4.0",
     "@testing-library/jest-dom": "^6.6.3",
     "@testing-library/user-event": "^14.6.1",
-    "jest": "^30.0.4",
+    "jest": "^30.2.0",
     "jest-environment-jsdom": "^30.0.4"
   }
 }