The Spot Price of the Market Index Is $900

The spot price of the market index is $900.A 3-month forward contract on this index is priced at $930.The market index rises to $920 by the expiration date.The annual rate of interest on treasuries is 2.4% (0.2% per month) .What is the difference in the payoffs between a long index investment and a long forward contract investment? (Assume monthly compounding.)

A) $10.84
B) $24.59
C) $26.40
D) $43.20