Task: Question Answering
Input (English): Question: Pipe A can fill a tank in 6 hours. Due to a leak at the bottom, it takes 9 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?

 Option A: 33

 Option B: 77

 Option C: 18

 Option D: 99

 Option E: 66
Output (English): Option C