Task: Question Answering
Input (English): Problem: pipe a can fill a tank in 5 hr , pipe b in 10 hr and pipe c in 30 hr . if all the pipes are open in how many hours will tank be filled ? 
Options: a ) 1 hr , b ) 2 hr , c ) 3 hr , d ) 4 hr , e ) 5 hr
Output (English): c