A sum of money deposited at C.I. amounts to Rs.1980 in 3 years and to Rs.2492 in 4 years. Find the rate percent?  Choose the correct answer:
A) 30 % B) 10 % C) 25 % D) 19 % E) 50 %

Rationale: "1980 - - - 512 100 - - - ? = > 25 % answer : c"
Answer: C