Task: Question Answering
Input (English): Problem: an electric pump can fill a tank in 3 hours . because of a leak in the tank , it took 3 hours 30 min to fill the tank . in what time the leak can drain out all the water of the tank and will make tank empty ? 
Options: a ) 10 hours , b ) 13 hours , c ) 17 hours , d ) 21 hours , e ) 25 hours
Output (English): d