diff --git a/index.js b/index.js
index f61169392..833f3628a 100644
--- a/index.js
+++ b/index.js
@@ -48,8 +48,8 @@ function processFirstItem(stringList, callback) {
  * [2] Invoking `processLength` passing `[]` and `(num) => "There are " + num`,
  * should return "There are 0".
 */
-function processLength(/* CODE HERE */) {
-  /* CODE HERE */
+function processLength(list,callback) {
+return callback(list.length);
 }
 
 /**
@@ -66,8 +66,9 @@ function processLength(/* CODE HERE */) {
  * Invoking `processLastItem` passing `['foo', 'bar']` and `(str) => str + str`,
  * should return 'barbar'.
 */
-function processLastItem(/* CODE HERE */) {
-  /* CODE HERE */
+function processLastItem(stringList,callback) {
+  const stringNum = stringList.length - 1;
+  return callback(stringList[stringNum])
 }
 
 /**
@@ -88,8 +89,8 @@ function processLastItem(/* CODE HERE */) {
  * [2] Invoking `processSum` passing `-5`, '-1', and `(num) => num + 1000`,
  * should return 994.
 */
-function processSum(/* CODE HERE */) {
-  /* CODE HERE */
+function processSum(num1, num2, callback) {
+  return callback (num1+ num2);
 }
 
 /**
@@ -110,8 +111,8 @@ function processSum(/* CODE HERE */) {
  * [2] Invoking `processProduct` passing 25 and 0 and `(num) => num + 1000`,
  * should return 1000.
 */
-function processProduct(/* CODE HERE */) {
-  /* CODE HERE */
+function processProduct(num1, num2, callback) {
+return callback (num1* num2)
 }
 
 /**
@@ -155,9 +156,14 @@ function processDuplicateFree(/* CODE HERE ONLY AFTER COMPLETING ALL OTHER TASKS
  * 
  * [2] Invoking `lowerCaseStrings` with `['a', 'b', 'c' ]` will return `[ 'a', 'b', 'c' ]`.
 */
-function lowerCaseStrings(/* code here */) {
-  /* code here */
-}
+function lowerCaseStrings(strings,) {
+const stringArr = [];
+  strings.forEach((strings) => {
+ stringArr.push(strings.toLowerCase());
+  })
+return stringArr;
+};
+
 
 /**
  * ### Challenge `isItAnApple`
@@ -174,10 +180,12 @@ function lowerCaseStrings(/* code here */) {
  * 
  * [2] Invoking `isItAnApple` with `['a', 'b', 'c' ]` will return `[ false, false, false ]`.
 */
-function isItAnApple(/* code here */) {
-  /* code here */
-}
+function isItAnApple(strings) {
+  
+ return( strings.map(strings =>  strings === 'apple' ? true : false))
 
+  
+}
 /**
  * ### Challenge `removeApple`
  * 
@@ -194,8 +202,10 @@ function isItAnApple(/* code here */) {
  * 
  * [2] Invoking `removeApple` with `['a', 'b', 'c' ]` will return `[ 'a', 'b', 'c' ]`.
 */
-function removeApple(/* code here */) {
-  /* code here */
+function removeApple(strings) {
+
+  return (strings.filter(string => string !== 'apple')
+  )
 }
 
 /**
@@ -213,10 +223,11 @@ function removeApple(/* code here */) {
  * 
  * [2] Invoking `stringSmash` with `['a', 'b', 'c' ]` will return `abc`.
 */
-function stringSmash(/* code here */) {
-  /* code here */
+function stringSmash(strings) {
+return strings.reduce((string,start)=>{return string += start},[]);
 }
 
+
 // A local community center is holding a fund raising 5k fun run and has invited
 // 50 small businesses to make a small donation on their behalf for some much needed
 // updates to their facilities. Each business has assigned a representative
@@ -232,8 +243,8 @@ function stringSmash(/* code here */) {
  * @returns an array with all the runners' full names in the following format: "Smith, John".
  * The full names appear in the array in the same order the runners appear in the `runners` array.
 */
-function getFullNames(/* CODE HERE */) {
-  /* CODE HERE */
+function getFullNames(runners) {
+  return (runners.map(arr => arr.last_name + ', ' + arr.first_name))
 }
 
 /**
@@ -248,8 +259,8 @@ function getFullNames(/* CODE HERE */) {
  * @returns an array with all the runners' first names in ALL CAPS.
  * The first names appear in the array in the same order the runners appear in the `runners` array.
 */
-function firstNamesAllCaps(/* CODE HERE */) {
-  /* CODE HERE */
+function firstNamesAllCaps(runners) {
+  return runners.map(names => names.first_name.toUpperCase())
 }
 
 /**
@@ -266,8 +277,8 @@ function firstNamesAllCaps(/* CODE HERE */) {
  * @returns an array containing only the runners that use the given `tShirtSize`.
  * The runners in the array appear in the same order they appear in the `runners` array.
 */
-function getRunnersByTShirtSize(/* CODE HERE */) {
-  /* CODE HERE */
+function getRunnersByTShirtSize(runners, tShirtSize) {
+  return (runners.filter(person => person.shirt_size === tShirtSize))
 }
 
 /**