Two pipes P and Q can fill a tank A in 10 hrs and 12 hrs respectively. A third pipe R can empty a tank B in 40 hrs. Tank B is two times in volume compared to tank A. If P and Q are kept open to fill tank A. If R is connected to empty tank A at the same time such that all the pipes operate simultaneously, how long will it take for the tank A to be fully filled?

Two pipes P and Q can fill a tank A in 10 hrs and 12 hrs respectively.

1.	Two pipes P and Q can fill a tank A in 10 hrs and 12 hrs respectively. A third pipe R can empty a tank B in 40 hrs. Tank B is two times in volume compared to tank A. If P and Q are kept open to fill tank A. If R is connected to empty tank A at the same time such that all the pipes operate simultaneously, how long will it take for the tank A to be fully filled?
A.	6 hrs 40 minutes
B.	8 hrs 30 minutes
C.	7 hrs 30 minutes
D.	None of the above
Answer» D. None of the above