diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..5467ea0e8 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -12,4 +12,6 @@ const address = {
   postcode: "XYZ 123",
 };
 
+// console.log(`${address[2]}`)
 console.log(`My house number is ${address[0]}`);
+
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..ecfa3c0e1 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,8 +1,12 @@
 // Predict and explain first...
+// TypeError: author is not iterable because A for...of loop is used for iterable things such as arrays, strings, Maps, and Sets.
+
+// But author is a plain object. Plain objects aren't directly iterable with for...of.
+
+// To loop through an object's values, use:
 
 // 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
-
 const author = {
   firstName: "Zadie",
   lastName: "Smith",
@@ -11,6 +15,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
-}
+}
\ No newline at end of file
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..0d9b65961 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,5 +1,7 @@
 // Predict and explain first...
-
+//  the code might print something like this bruschetta serves 2
+//ingredients: [object Object] because the ${recipe} is an object and we only trying to print the 
+// ingredients inside the object
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
 // How can you fix it?
@@ -11,5 +13,5 @@ const recipe = {
 };
 
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+ingredients:
+${recipe.ingredients.join("\n")}`);
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..078449f3c 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,11 @@
-function contains() {}
+function contains(object, property) {
+  if (typeof object !== "object" || object === null || Array.isArray(object)) {
+    return false;
+  }
+
+  return Object.hasOwn(object, property);
+}
 
 module.exports = contains;
+
+
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..52d343f5c 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -21,15 +21,26 @@ as the object doesn't contains a key of 'c'
 // When passed to contains
 // Then it should return false
 test.todo("contains on empty object returns false");
-
+test("contains on empty object returns false", () => {
+  expect(contains({}, "a")).toBe(false);
+});
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
-
+test("contains returns true when property exists", () => {
+  expect(contains({ a: 1, b: 2 }, "a")).toBe(true);
+});
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
+test("contains returns false when property does not exist", () => {
+  expect(contains({ a: 1, b: 2 }, "c")).toBe(false);
+});
+
 
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("contains returns false when passed an array", () => {
+  expect(contains([], "a")).toBe(false);
+});
\ No newline at end of file
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..71b45e605 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,15 @@
-function createLookup() {
+function createLookup(countryCurrencyPairs) {
   // implementation here
+  const lookup = {};
+
+  for (const pair of countryCurrencyPairs) {
+    const [countryCode, currencyCode] = pair;
+    lookup[countryCode] = currencyCode;
+  }
+
+  return lookup;
 }
 
 module.exports = createLookup;
+
+module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..245a1e158 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -33,3 +33,14 @@ It should return:
    'CA': 'CAD'
  }
 */
+test("creates a country currency code lookup for multiple codes", () => {
+  const countryCurrencyPairs = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  expect(createLookup(countryCurrencyPairs)).toEqual({
+    US: "USD",
+    CA: "CAD",
+  });
+});
\ No newline at end of file
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..f75f93a10 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,13 +1,50 @@
 function parseQueryString(queryString) {
   const queryParams = {};
+
+  // If the query string is empty, return an empty object
   if (queryString.length === 0) {
     return queryParams;
   }
+
+  // Split the query string into separate key-value pairs
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+    // Ignore empty pairs
+    if (pair === "") {
+      continue;
+    }
+
+    // Find the first "="
+    const equalsPosition = pair.indexOf("=");
+
+    let key;
+    let value;
+
+    // If there is no "="
+    if (equalsPosition === -1) {
+      key = pair;
+      value = "";
+    } else {
+      // Everything before "=" is the key
+      key = pair.substring(0, equalsPosition);
+
+      // Everything after the first "=" is the value
+      value = pair.substring(equalsPosition + 1);
+    }
+
+    // Replace "+" with spaces and decode special characters
+    key = decodeURIComponent(key.replace(/\+/g, " "));
+    value = decodeURIComponent(value.replace(/\+/g, " "));
+
+    // If the key already exists, store multiple values in an array
+    if (queryParams[key] === undefined) {
+      queryParams[key] = value;
+    } else if (Array.isArray(queryParams[key])) {
+      queryParams[key].push(value);
+    } else {
+      queryParams[key] = [queryParams[key], value];
+    }
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..28b2d5288 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,21 @@
-function tally() {}
+function tally(items) {
+  // Check that the input is an array
+  if (!Array.isArray(items)) {
+    throw new Error("Input must be an array");
+  }
+
+  const counts = {};
+
+  // Go through each item in the array
+  for (const item of items) {
+    if (counts[item] === undefined) {
+      counts[item] = 1;
+    } else {
+      counts[item] = counts[item] + 1;
+    }
+  }
+
+  return counts;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..bea83034a 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -24,11 +24,23 @@ const tally = require("./tally.js");
 // When passed to tally
 // Then it should return an empty object
 test.todo("tally on an empty array returns an empty object");
-
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+test("tally counts duplicate items", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({
+    a: 2,
+    b: 1,
+    c: 1,
+  });
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test("tally throws an error when given a string", () => {
+  expect(() => tally("hello")).toThrow();
+});
\ No newline at end of file
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..55329026b 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -10,20 +10,28 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
+module.exports = invert
 
 // a) What is the current return value when invert is called with { a : 1 }
+// {key: 1} because the invertedObj,ket = value does not use the variable key
+
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+// {key:2} the loop runs twice and the second iteration replaces the first one so the answer becomes 2
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// The target return value is to swap the keys and values so {a:1, b:2} becomes {1:a, 2:b}
 
 // c) What does Object.entries return? Why is it needed in this program?
+// Object.entries() turns an object into an array containing key-value pairs
 
 // d) Explain why the current return value is different from the target output
-
+// invertedObj.key means to create or access an object called key 
+// and inverted invertedObj[key] means to use whatever value is stored in the key variable 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..2db3aa954
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,21 @@
+const invert = require("./invert.js");
+
+test("inverts an object with one property", () => {
+  expect(invert({ a: 1 })).toEqual({
+    1: "a",
+  });
+});
+
+test("inverts an object with multiple properties", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({
+    1: "a",
+    2: "b",
+  });
+});
+
+test("inverts the example object", () => {
+  expect(invert({ x: 10, y: 20 })).toEqual({
+    10: "x",
+    20: "y",
+  });
+});