What will be the difference between simple and compound interest at 10% per annum on a sum of Rs. 1000 after 4 years? Choose the correct choice
A) rs . 31 B) rs . 32.10 C) rs . 40.40 D) rs . 64.10 E) rs . 74.10

Rationale: "s . i . = ( 1000 * 10 * 4 ) / 100 = rs . 400 c . i . = [ 1000 * ( 1 + 10 / 100 ) 4 - 1000 ] = rs . 464.10 difference = ( 464.10 - 400 ) = rs . 64.10 answer : d"
Answer: D