If a pipe can empty a full tank in y hours: then part emptied in 1 hour.

If a pipe can empty a full tank in y hours: then part emptied in 1hour.

A tank 9 ft by 5 ft by 2 ft is fitted with an inlet pipe and an exhaust pipe.The inlet pipe pours in 576 cu.Inch of water per minute and the exhaust pipe can empty the full tank in 3 hours.If the tank is full and both pipes are open,how many hours will it take to empty it?

Pipe A can fill an empty tank in 5 hours while pipe B can empty the full tank in 6 hours.If both are opened at the same time in the empty tank,how much time will they take to fill it up completely?