Task: Question Answering
Input (English): Problem: two pipes p and q can fill a cistern in 12 and 15 minutes respectively. both are opened together, but at the end of 2 minutes the first is turned off. how many more minutes will it take for the cistern to fill after the first pipe is turned off ?
Options: a. 8.5, b. 9.5, c. 10.5, d. 11.5, e. 12.5
Output (English): c