An investment yields an interest payment of $234 each month. If the simple annual interest rate is 9%, what is the amount of the investment?
Choose the correct choice from the following options
A) $ 28,300
B) $ 30,400
C) $ 31,300
D) $ 31,200
E) $ 35,100

Rationale: let the principal amount = p simple annual interest = 9 % simple monthly interest = ( 9 / 12 ) = ( 3 / 4 ) % ( 3 / 4 ) * ( p / 100 ) = 234 = > p = ( 234 * 4 * 10 ^ 2 ) / 3 = 78 * 4 * 10 ^ 2 = 312 * 10 ^ 2 = 31200 answer d
Answer: D