The amount of principal Rs.8000 at compound interest at the ratio of 5% p.a. for 3 years is  Choose the correct answer.
A) rs . 9621  B) rs . 6921  C) rs . 9261  D) rs . 6261  E) rs . 6361

Rationale: "c . i = p ( 1 + r / 100 ) ^ n = 8000 ( 1 + 5 / 100 ) ^ 3 = 8000 ( 21 / 20 * 21 / 20 * 21 / 20 ) = rs 9261 answer : c"
Answer: C