diff --git a/assignments/callbacks.js b/assignments/callbacks.js
index d5028657e..0ff7ed0b6 100644
--- a/assignments/callbacks.js
+++ b/assignments/callbacks.js
@@ -1,48 +1,72 @@
 // Create a callback function and invoke the function to test your work. You have been provided an example of a problem and a solution to see how this works with our items array.  Study both the problem and the solution to figure out the rest of the problems.
 
-const items = ['Pencil', 'Notebook', 'yo-yo', 'Gum'];
+const items = ["Pencil", "Notebook", "yo-yo", "Gum"];
 
-/* 
+// //Given this problem:
 
-  //Given this problem: 
-  
-  function firstItem(arr, cb) {
-    // firstItem passes the first item of the given array to the callback function.
-  }
+// function firstItem(arr, cb) {
+//   // firstItem passes the first item of the given array to the callback function.
+// }
 
-  // Potential Solution:
-  function firstItem(arr, cb) {
-    return cb(arr[0]);
-  }
+// Potential Solution:
+// function firstItem(arr, cb) {
+//   return cb(arr[0]);
+// }
 
-  firstItem(items, function(first) {
-    console.log(first)
-  });
+// firstItem(items, function(first) {
+//   console.log(first);
+// });
 
-*/
+// function getLength(arr, cb) {
+//   // getLength passes the length of the array into the callback.
+//   return cb(arr.length);
+// }
 
+// getLength(items, function(length) {
+//   console.log(length);
+// });
 
-function getLength(arr, cb) {
-  // getLength passes the length of the array into the callback.
-}
+// function last(arr, cb) {
+//   // last passes the last item of the array into the callback.
+//   return cb(arr[arr.length - 1]);
+// }
 
-function last(arr, cb) {
-  // last passes the last item of the array into the callback.
-}
+// last(items, function(lastItem) {
+//   console.log(lastItem);
+// });
 
-function sumNums(x, y, cb) {
-  // sumNums adds two numbers (x, y) and passes the result to the callback.
-}
+// function sumNums(x, y, cb) {
+//   // sumNums adds two numbers (x, y) and passes the result to the callback.
+//   return cb(x + y);
+// }
 
-function multiplyNums(x, y, cb) {
-  // multiplyNums multiplies two numbers and passes the result to the callback.
-}
+// sumNums(2, 3, function(sum) {
+//   console.log(sum);
+// });
+
+// function multiplyNums(x, y, cb) {
+//   // multiplyNums multiplies two numbers and passes the result to the callback.
+//   return cb(x * y);
+// }
+
+// multiplyNums(3, 2, function(multiply) {
+//   console.log(multiply);
+// });
 
 function contains(item, list, cb) {
   // contains checks if an item is present inside of the given array/list.
   // Pass true to the callback if it is, otherwise pass false.
+  if (list.indexOf(item) != -1) {
+    return cb(true);
+  } else {
+    return cb(false);
+  }
 }
 
+contains("Pencil", items, function(bool) {
+  console.log(bool);
+});
+
 /* STRETCH PROBLEM */
 
 function removeDuplicates(array, cb) {