A sum amounts to Rs.8820 in 2 years at the rate of 5% p.a. If interest was compounded yearly then what was the principal?
Select:  A) s . 4000  B) s . 5000  C) s . 4500  D) s . 4800  E) s . 8000

Rationale: "ci = 8820 , r = 5 , n = 2 ci = p [ 1 + r / 100 ] ^ 2 = p [ 1 + 5 / 100 ] ^ 2 8820 = p [ 21 / 20 ] ^ 2 8820 [ 20 / 21 ] ^ 2 8000 answer : e"
Answer: E