Pipes A and B can fill a tank in 12 h and 18 h, respectively, whereas pipe C can empty the full tank in 8 h. A and B opened for h and then closed. C alone will empty the tank in (in h):
A pump can fill a tank with water in 1 hour. Because of a leak, it took hours to fill the tank. In how many hours can the leak alone drain all the water of the tank when it is full?