A sum of ₹ 15,600 is invested partly at 7% per annum and the remaining at 9% per annum simple interest. If the total interest at the end of 3 years is ₹ 3,738. how much money was invested at 7% per annum?

A

₹ 7,800

B

₹ 7,900

C

₹ 7,600

D

₹ 7,700