A sum of money at simple interest amounts to Rs. 800 in 3 years and to Rs. 850 in 4 years. The sum is:	Choose the correct choice:
A) Rs. 670
B) Rs. 690
C) Rs. 600
D) Rs. 625
E) Rs. 654
Explanation:   S.I. for 1 year = Rs. (850 - 800) = Rs. 50.   S.I. for 3 years = Rs.(50 x 3) = Rs. 150.   Principal = Rs. (800 - 150) = Rs. 600.   Answer: Option Rs. 600
<result>C</result>
A sum of money at simple interest amounts to Rs. 800 in 3 years and to Rs. 850 in 4 years. The sum is: