Task: Question Answering
Input (English): Question: Pumping alone at their respective constant rates, one inlet pipe fills an empty tank to 1/4 of capacity in 9 hours and a second inlet pipe fills the same empty tank to 2/3 of capacity in 6 hours. How many hours will it take both pipes, pumping simultaneously at their respective constant rates, to fill the empty tank to capacity?

 Option A: 3.25

 Option B: 3.6

 Option C: 4.2

 Option D: 4.4

 Option E: 7.2
Output (English): Option E