Write a function that computes the factorial of n (often denoted n!), i.e. the product n(n-1)(n-2)...(3)(2)(1). Your function should use a for loop and an accumulator. You may assume the factorial of zero is one. For example, when n = 6, your code should compute 1*2*3*4*5*6. When n = 7, your code should compute 1*2*3*4*5*6*7, which is (1*2*3*4*5*6)*7.