A certain sum is invested at simple interest at 15% p.a. for two years instead of investing at 12% p.a. for the same time period. Therefore the interest received is more by Rs. 420. Find the sum?	Choose the correct choice from the following choices.
A) s . 5000	B) s . 7000	C) s . 14000	D) s . 17000	E) s . 27000

Rationale: "let the sum be rs . x . ( x * 15 * 2 ) / 100 - ( x * 12 * 2 ) / 100 = 420 = > 30 x / 100 - 24 x / 100 = 420 = > 6 x / 100 = 420 = > x = 7000 . answer : b"
Answer: B