Task: Question Answering
Input (English): Problem: pipe a fills a tank in 20 minutes . pipe b can fill the same tank 4 times as fast as pipe a . if both the pipes are kept open when the tank is empty , how many minutes will it take to fill the tank ? 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 5 , e ) 6
Output (English): c