A sum was invested for 4 yr at a certain rate of simple interest. If it had been invested at 2% more annual rate of interest, then Rs. 64 more would have been obtained. What is the sum?
(a) Rs.600
(b) Rs.700
(c) Rs.800
(d) Rs.900
(a) Rs.600
(b) Rs.700
(c) Rs.800
(d) Rs.900