A sum of money lent out at S.I. amounts to Rs. 780 after 2 years and to Rs. 1020 after a further period of 5 years. The sum is?  Pick:
A) s . 684 B) s . 500 C) s . 540 D) s . 740 E) s . 840

Rationale: "s . i for 5 years = ( 1020 - 780 ) = rs . 240 . s . i . for 2 years = 240 / 5 * 2 = rs . 96 . principal = ( 780 - 96 ) = rs . 684 answer : a"
Answer: A