Answer:
$ 637.17
Explanation:
First, let's convert the interest per year (iy) to interest per month (im):
(1 + im)¹² = 1 + iy
(1 + im)¹² = 1 + 0.08
1 + im =

1 + im = 1.00643
im = 0.00643
im = 0.643%
The total amount (A) of an investment is:

Where R is the amount invested per month, and n the number of monthes. So:

10,000 = R*15.6943
R = $ 637.17