The Simple Interest Earned by a Certain Amount of Money

Multiple Choice

The simple interest earned by a certain amount of money varies jointly as the rate of interest and the time (in years) that the money is invested. If the money is invested at 15% for 5 years, $600 is earned. How much is earned if the money is invested at 20% for 7 years?

A) I = $1134
B) I = $1117
C) I = $1126
D) I = $1113
E) I = $1120