If the compound interest on a certain sum of money for 4 years at 10% per annum be Rs. 993, what would be the simple interest? Choose the most appropriate option.
A) rs . 880 B) rs . 890 C) rs . 1200 D) rs . 900 E) none

Rationale: "let p = principal a - amount we have a = p ( 1 + r / 100 ) 3 and ci = a - p atq 993 = p ( 1 + r / 100 ) 3 - p ? p = 3000 / - now si @ 10 % on 3000 / - for 4 yrs = ( 3000 x 10 x 4 ) / 100 = 1200 / - answer : c ."
Answer: C