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