suresh borrowed some money at the rate of 12 % p . a . for the first 3 years , 9 % p . a . for the next 5 years and 13 % p . a . for the period beyond 8 years . if the total interest paid by him at the end of 11 years is rs . 8160 , how much money did he borrow ?  Choose the correct answer:
A) s . 8500	B) s . 6000	C) s . 6800	D) s . 9000	E) s . 7000

Rationale: using the formula s . i = p * t * r / 100 ( x * 12 * 3 / 100 ) + ( x * 9 * 5 / 100 ) + ( x * 13 * 3 / 100 ) = 8160 x = 6800 i . e money borrowed is rs . 6800 answer : c
Answer: C