A sum of money at simple interest amounts to Rs. 840 in 3 years and to Rs. 854 in 4 years. The sum is:  Choose the correct choice from the following
A) 647	B) 798	C) 654	D) 847	E) 976

Rationale: "s . i . for 1 year = rs . ( 854 - 840 ) = rs . 14 . s . i . for 3 years = rs . ( 14 x 3 ) = rs . 42 . principal = rs . ( 840 - 42 ) = rs . 798 . answer : b"
Answer: B