An investment yields an interest payment of $216 each month. If the simple annual interest rate is 9%, what is the amount of the investment? Choose the correct choice
A) $ 28,300  B) $ 30,400  C) $ 28,800  D) $ 32,500  E) $ 35,100

Rationale: "let the principal amount = p simple annual interest = 9 % simple monthly interest = ( 9 / 12 ) = ( 3 / 4 ) % ( 3 / 4 ) * ( p / 100 ) = 216 = > p = ( 216 * 4 * 10 ^ 2 ) / 3 = 72 * 4 * 10 ^ 2 = 288 * 10 ^ 2 = 28800 answer c"
Answer: C