Task: Question Answering
Input (English): Problem: a cistern is filled by a tap in 7 1 / 2 hours . due to leak in the bottom of the cistern , it takes half an hour longer to fill the cistern . if the cistern is full how many hours will it take the leak to empty it ? 
Options: a ) 80 , b ) 100 , c ) 120 , d ) 140 , e ) 160
Output (English): c