diff --git a/08_calculator/calculator.spec.js b/08_calculator/calculator.spec.js
index 3507452..48b08c9 100644
--- a/08_calculator/calculator.spec.js
+++ b/08_calculator/calculator.spec.js
@@ -1,77 +1,77 @@
 const calculator = require('./calculator');
 
 describe('add', () => {
-	test('adds 0 and 0', () => {
-		expect(calculator.add(0,0)).toBe(0);
-	});
+  test('adds 0 and 0', () => {
+    expect(calculator.add(0, 0)).toBe(0);
+  });
 
-	test.skip('adds 2 and 2', () => {
-		expect(calculator.add(2,2)).toBe(4);
-	});
+  test.skip('adds 2 and 2', () => {
+    expect(calculator.add(2, 2)).toBe(4);
+  });
 
-	test.skip('adds positive numbers', () => {
-		expect(calculator.add(2,6)).toBe(8);
-	});
+  test.skip('adds positive numbers', () => {
+    expect(calculator.add(2, 6)).toBe(8);
+  });
 });
 
 describe('subtract', () => {
-	test.skip('subtracts numbers', () => {
-		expect(calculator.subtract(10,4)).toBe(6);
-	});
+  test.skip('subtracts numbers', () => {
+    expect(calculator.subtract(10, 4)).toBe(6);
+  });
 });
 
 describe('sum', () => {
-	test.skip('computes the sum of an empty array', () => {
-		expect(calculator.sum([])).toBe(0);
-	});
+  test.skip('computes the sum of an empty array', () => {
+    expect(calculator.sum([])).toBe(0);
+  });
 
-	test.skip('computes the sum of an array of one number', () => {
-		expect(calculator.sum([7])).toBe(7);
-	});
+  test.skip('computes the sum of an array of one number', () => {
+    expect(calculator.sum([7])).toBe(7);
+  });
 
-	test.skip('computes the sum of an array of two numbers', () => {
-		expect(calculator.sum([7,11])).toBe(18);
-	});
+  test.skip('computes the sum of an array of two numbers', () => {
+    expect(calculator.sum([7, 11])).toBe(18);
+  });
 
-	test.skip('computes the sum of an array of many numbers', () => {
-		expect(calculator.sum([1,3,5,7,9])).toBe(25);
-	});
+  test.skip('computes the sum of an array of many numbers', () => {
+    expect(calculator.sum([1, 3, 5, 7, 9])).toBe(25);
+  });
 });
 
 describe('multiply', () => {
-	test.skip('multiplies two numbers', () => {
-		expect(calculator.multiply(2,4)).toBe(8);
-	});
+  test.skip('multiplies two numbers', () => {
+    expect(calculator.multiply([2, 4])).toBe(8);
+  });
 
-	test.skip('multiplies several numbers', () => {
-		expect(calculator.multiply(2,4,6,8,10,12,14)).toBe(645120);
-	});
+  test.skip('multiplies several numbers', () => {
+    expect(calculator.multiply([2, 4, 6, 8, 10, 12, 14])).toBe(645120);
+  });
 });
 
 describe('power', () => {
-	test.skip('raises one number to the power of another number', () => {
-		expect(calculator.power(4,3)).toBe(64); // 4 to third power is 64
-	});
+  test.skip('raises one number to the power of another number', () => {
+    expect(calculator.power(4, 3)).toBe(64); // 4 to third power is 64
+  });
 });
 
 describe('factorial', () => {
-	test.skip('computes the factorial of 0', () => {
-		expect(calculator.factorial(0)).toBe(1); // 0! = 1
-	});
+  test.skip('computes the factorial of 0', () => {
+    expect(calculator.factorial(0)).toBe(1); // 0! = 1
+  });
 
-	test.skip('computes the factorial of 1', () => {
-		expect(calculator.factorial(1)).toBe(1);
-	});
+  test.skip('computes the factorial of 1', () => {
+    expect(calculator.factorial(1)).toBe(1);
+  });
 
-	test.skip('computes the factorial of 2', () => {
-		expect(calculator.factorial(2)).toBe(2);
-	});
+  test.skip('computes the factorial of 2', () => {
+    expect(calculator.factorial(2)).toBe(2);
+  });
 
-	test.skip('computes the factorial of 5', () => {
-		expect(calculator.factorial(5)).toBe(120);
-	});
+  test.skip('computes the factorial of 5', () => {
+    expect(calculator.factorial(5)).toBe(120);
+  });
 
-	test.skip('computes the factorial of 10', () => {
-		expect(calculator.factorial(10)).toBe(3628800);
-	});
+  test.skip('computes the factorial of 10', () => {
+    expect(calculator.factorial(10)).toBe(3628800);
+  });
 });
diff --git a/08_calculator/solution/calculator-solution.js b/08_calculator/solution/calculator-solution.js
index ab39a60..b195387 100644
--- a/08_calculator/solution/calculator-solution.js
+++ b/08_calculator/solution/calculator-solution.js
@@ -10,13 +10,9 @@ const sum = function (array) {
   return array.reduce((total, current) => total + current, 0);
 };
 
-const multiply = function(...args){
-  let product = 1;
-  for (let i = 0; i < args.length; i++) {
-    product *= args[i];
-  }
-  return product;
- };
+const multiply = function (array) {
+  return array.reduce((product, current) => product * current)
+};
 
 const power = function (a, b) {
   return Math.pow(a, b);