Task: Question Answering
Input (English): Problem: two pipes can separately fill a tank in 20 and 30 hours respectively . both the pipes are opened to fill the tank but when the tank is full , a leak develops in the tank through which one - third of water supplied by both the pipes goes out . what is the total time taken to fill the tank ? 
Options: a ) 17 hrs , b ) 16 hrs , c ) 15 hrs , d ) 13 hrs , e ) 12 hrs
Output (English): b