Task: Question Answering
Input (English): Problem: a tank is filled in 10 hours by 3 pipes a , b and c . the pipe c is twice as fast as b and b is twice as fast as a . how much time will pipe a alone take to fill the tank ? 
Options: a ) 70 hours , b ) 30 hours , c ) 35 hours , d ) 50 hours , e ) 60 hours
Output (English): a