Task: Question Answering
Input (English): Problem: 5 pumps , working 9 hours a day , can empty a tank in 3 days . how many hours a day should 6 pumps work in order to empty the tank in 1 day ? 
Options: a ) 20 hours , b ) 22.5 hours , c ) 23 hours , d ) 23.5 hours , e ) 24 hours
Output (English): b