A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is :________?

A. Rs. 700
B. Rs. 690
C. Rs. 650
D. Rs. 698

Simple Interest (SI) for 1 year = 854-815 = 39
Simple Interest (SI) for 3 years = 39 × 3 = 117
Principal = 815 – 117 = Rs.698