Task: Question Answering
Input (English): Problem: 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 ? 
Options: a ) 5 % , b ) 6 % , c ) 7 % , d ) 8 % , e ) 9 %
Output (English): a