diff --git a/index.js b/index.js
index 3df06ec1..51d8d9b1 100644
--- a/index.js
+++ b/index.js
@@ -7,7 +7,11 @@
  * trimProperties({ name: '  jane  ' }) // returns a new object { name: 'jane' }
  */
 function trimProperties(obj) {
-  // ✨ implement
+  const result = {}
+  for (let prop in obj) {
+    result[prop] = obj[prop].trim()
+  }
+  return result
 }
 
 /**
@@ -19,7 +23,10 @@ function trimProperties(obj) {
  * trimPropertiesMutation({ name: '  jane  ' }) // returns the object mutated in place { name: 'jane' }
  */
 function trimPropertiesMutation(obj) {
-  // ✨ implement
+  for (let prop in obj) {
+    obj[prop] = obj[prop].trim()
+  }
+  return obj
 }
 
 /**
@@ -31,7 +38,13 @@ function trimPropertiesMutation(obj) {
  * findLargestInteger([{ integer: 1 }, { integer: 3 }, { integer: 2 }]) // returns 3
  */
 function findLargestInteger(integers) {
-  // ✨ implement
+  let result = integers[0].integer
+  for (let idx = 1; idx < integers.length; idx++) {
+    if (integers[idx].integer > result) {
+      result = integers[idx].integer
+    }
+  }
+  return result
 }
 
 class Counter {
@@ -40,7 +53,7 @@ class Counter {
    * @param {number} initialNumber - the initial state of the count
    */
   constructor(initialNumber) {
-    // ✨ initialize whatever properties are needed
+    this.count = initialNumber
   }
 
   /**
@@ -56,7 +69,10 @@ class Counter {
    * counter.countDown() // returns 0
    */
   countDown() {
-    // ✨ implement
+    if (this.count > 0) {
+      return this.count--
+    }
+    return this.count
   }
 }
 
@@ -65,7 +81,8 @@ class Seasons {
    * [Exercise 5A] Seasons creates a seasons object
    */
   constructor() {
-    // ✨ initialize whatever properties are needed
+    this.seasons = ['summer', 'fall', 'winter', 'spring']
+    this.currentSeason = 0
   }
 
   /**
@@ -81,7 +98,13 @@ class Seasons {
    * seasons.next() // returns "summer"
    */
   next() {
-    // ✨ implement
+    const result = this.seasons[this.currentSeason]
+    if (this.currentSeason === 3) {
+      this.currentSeason = 0
+    } else {
+      ++this.currentSeason
+    }
+    return result
   }
 }
 
diff --git a/index.test.js b/index.test.js
index cfb0a0b3..93322d38 100644
--- a/index.test.js
+++ b/index.test.js
@@ -8,16 +8,33 @@ describe('[Exercise 1] trimProperties', () => {
     const actual = utils.trimProperties(input)
     expect(actual).toEqual(expected)
   })
-  // test('[2] returns a copy, leaving the original object intact', () => {})
+   test('[2] returns a copy, leaving the original object intact', () => {
+    const input = { foo: '  foo ', bar: 'bar ', baz: ' baz' } 
+    utils.trimProperties(input)
+    expect(input).toEqual({ foo: '  foo ', bar: 'bar ', baz: ' baz'} )
+   })
 })
 
 describe('[Exercise 2] trimPropertiesMutation', () => {
-  // test('[3] returns an object with the properties trimmed', () => {})
-  // test('[4] the object returned is the exact same one we passed in', () => {})
+   test('[3] returns an object with the properties trimmed', () => {
+    const input = { foo: '  foo ', bar: 'bar ', baz: ' baz' }
+    const expected = { foo: 'foo', bar: 'bar', baz: 'baz' }
+    const actual = utils.trimProperties(input)
+    expect(actual).toEqual(expected)
+   })
+   test('[4] the object returned is the exact same one we passed in', () => {
+    const input = { foo: '  foo ', bar: 'bar ', baz: ' baz' }
+    const actual = utils.trimPropertiesMutation(input)
+    expect(actual).toBe(input)
+   })
 })
 
 describe('[Exercise 3] findLargestInteger', () => {
-  // test('[5] returns the largest number in an array of objects { integer: 2 }', () => {})
+   test('[5] returns the largest number in an array of objects { integer: 2 }', () => {
+     const input = [{ integer: 1 }, { integer: 3 }, { integer: 2 }]
+     const actual = utils.findLargestInteger(input)
+     expect(actual).toBe(3)
+   })
 })
 
 describe('[Exercise 4] Counter', () => {
@@ -25,9 +42,20 @@ describe('[Exercise 4] Counter', () => {
   beforeEach(() => {
     counter = new utils.Counter(3) // each test must start with a fresh couter
   })
-  // test('[6] the FIRST CALL of counter.countDown returns the initial count', () => {})
-  // test('[7] the SECOND CALL of counter.countDown returns the initial count minus one', () => {})
-  // test('[8] the count eventually reaches zero but does not go below zero', () => {})
+   test('[6] the FIRST CALL of counter.countDown returns the initial count', () => {
+     expect(counter.countDown()).toBe(3)
+   })
+   test('[7] the SECOND CALL of counter.countDown returns the initial count minus one', () => {
+    counter.countDown()
+    expect(counter.countDown()).toBe(2)
+   })
+   test('[8] the count eventually reaches zero but does not go below zero', () => {
+    counter.countDown()
+    counter.countDown()
+    counter.countDown()
+    counter.countDown()
+    expect(counter.countDown()).toBe(0)
+   })
 })
 
 describe('[Exercise 5] Seasons', () => {
@@ -35,12 +63,37 @@ describe('[Exercise 5] Seasons', () => {
   beforeEach(() => {
     seasons = new utils.Seasons() // each test must start with fresh seasons
   })
-  // test('[9] the FIRST call of seasons.next returns "summer"', () => {})
-  // test('[10] the SECOND call of seasons.next returns "fall"', () => {})
-  // test('[11] the THIRD call of seasons.next returns "winter"', () => {})
-  // test('[12] the FOURTH call of seasons.next returns "spring"', () => {})
-  // test('[13] the FIFTH call of seasons.next returns again "summer"', () => {})
-  // test('[14] the 40th call of seasons.next returns "spring"', () => {})
+   test('[9] the FIRST call of seasons.next returns "summer"', () => {
+    expect(seasons.next()).toBe('summer')
+   })
+   test('[10] the SECOND call of seasons.next returns "fall"', () => {
+    seasons.next()
+    expect(seasons.next()).toBe('fall')
+   })
+   test('[11] the THIRD call of seasons.next returns "winter"', () => {
+    seasons.next()
+    seasons.next()
+    expect(seasons.next()).toBe('winter')
+   })
+   test('[12] the FOURTH call of seasons.next returns "spring"', () => {
+    seasons.next()
+    seasons.next()
+    seasons.next()
+    expect(seasons.next()).toBe('spring')
+   })
+   test('[13] the FIFTH call of seasons.next returns again "summer"', () => {
+    seasons.next()
+    seasons.next()
+    seasons.next()
+    seasons.next()
+    expect(seasons.next()).toBe('summer')
+   })
+   test('[14] the 40th call of seasons.next returns "spring"', () => {
+     for (let i = 0; i < 39; i++) {
+       seasons.next()
+     }
+     expect(seasons.next()).toBe('spring')
+   })
 })
 
 describe('[Exercise 6] Car', () => {
@@ -48,13 +101,13 @@ describe('[Exercise 6] Car', () => {
   beforeEach(() => {
     focus = new utils.Car('focus', 20, 30) // each test must start with a fresh car
   })
-  // test('[15] driving the car returns the updated odometer', () => {})
-  // test('[16] driving the car uses gas', () => {})
-  // test('[17] refueling allows to keep driving', () => {})
-  // test('[18] adding fuel to a full tank has no effect', () => {})
+   test('[15] driving the car returns the updated odometer', () => {})
+   test('[16] driving the car uses gas', () => {})
+   test('[17] refueling allows to keep driving', () => {})
+   test('[18] adding fuel to a full tank has no effect', () => {})
 })
 
 describe('[Exercise 7] isEvenNumberAsync', () => {
-  // test('[19] resolves true if passed an even number', () => {})
-  // test('[20] resolves false if passed an odd number', () => {})
+   test('[19] resolves true if passed an even number', () => {})
+   test('[20] resolves false if passed an odd number', () => {})
 })