An investment yields an interest payment of $231 each month. If the simple annual interest rate is 9%, what is the amount of the investment?	Choose the correct choice from the following:
A) $ 28,300	B) $ 30,800	C) $ 31,300	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 ) = 230 = > p = ( 231 * 4 * 10 ^ 2 ) / 3 = 77 * 4 * 10 ^ 2 = 308 * 10 ^ 2 = 30800 answer b"
Answer: B