Task: Question Answering
Input (English): Problem: a water tank is three - fifths full . pipe a can fill a tank in 10 minutes and pipe b can empty it in 6 minutes . if both the pipes are open , how long will it take to empty or fill the tank completely ? 
Options: a ) 6 min , b ) 8 min , c ) 7 min , d ) 9 min , e ) 1 min
Output (English): d