A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is:  Choose the correct choice from the following answers:
A) 500  B) 698  C) 780  D) 910  E) None
Sol.   S.I. for 1 year = Rs. (854 - 815) = Rs. 39.   S.I. for 3 years = Rs. (39 * 3) = Rs. 117.   ∴ Principal = Rs. (815 - 117) = Rs. 698   Answer 698
<result>B</result>
A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is: