The difference between C.I. and S.I. on an amount of $20,000 for 2 years is $98. What is the rate of interest per annum? Choose the correct choice from the following answers:
A) 9% B) 8% C) 7% D) 6% E) 5%
$98 is the interest on the first year of interest.   Let x be the interest rate.   The interest after the first year is 20000*x.   The interest on the first year's interest is 20000*x*x   20000*x^2 = 98   x = 0.07   The answer is 7%.
<result>C</result>
The difference between C.I. and S.I. on an amount of $20,000 for 2 years is $98. What is the rate of interest per annum?