The simple Interest on a certain sum of money at the rate of 4% p.a. for 5 years is Rs. 1680. At what rate of interest the same amount of interest can be received on the same sum after 4 years ?	Select the correct option
A) 5 %  B) 6 %  C) 7 %  D) 8 %  E) 9 %

Rationale: s . i . = 1680 , r = 4 % t = 5 years principal = ( 100 * 1680 ) / ( 5 * 4 ) = 8400 so p = 8400 rate = ( 100 * 1680 ) / ( 8400 * 4 ) = 5 % answer : a
Answer: A