Task: Question Answering
Input (English): Problem: the simple interest and the true discount on a certain sum for a given time and at a given rate are rs . 85 and rs . 80 respectively . the sum is : 
Options: a ) rs . 1800 , b ) rs . 1450 , c ) rs . 1360 , d ) rs . 6800 , e ) none
Output (English): c