The C.I. on a certain sum for 2 years Rs.41 and the simple interest is Rs.40. What is the rate percent?

The C.I. on a certain sum for 2 years Rs.41 and the simple interest is Rs.40. What is the rate percent?

A. 4%
B. 5%
C. 6%
D. 8%
Explanation:
SI = 20 + 20
CI = 20 + 21
20 —- 1
100 —- ? => 5%