Two inlet pipes P and Q can fill a tank in 10 hours and 12 hours separately. There is an outlet R that can let out water from the tank fully in 30 hours. If all the pipes are opened simultaneously, how much time will it take to fill the tank completely?

A

5 hours 30 minutes

B

6 hours 40 minutes

C

14 hours 45 minutes

D

6 hours 30 minutes