Two pumps are connected to an empty tank. Pump X fills the tank with water at a constant rate, while pump Y drains water out of the tank at a constant rate. The two pumps finish filling the tank in three times the duration it would take pump X alone to fill the tank. If pump Y alone can empty a whole tank in 36 minutes, then how many minutes does it take pump X alone to fill the tank?  Choose the correct choice from the following:
A) 18
B) 24
C) 26
D) 28
E) 30
Let V be the volume of the tank.   Let R be the rate per minute that pump X fills the tank.   Let T be the time it takes pump X to fill the tank.   The rate at which pump Y empties the tank is V/36 per minute.   (R - V/36)*3T=V=RT.   (R-V/36)*3=R   2R=V/12.   R=V/24.   It takes pump X 24 minutes to fill the tank.   The answer is 24.
<result>B</result>
Two pumps are connected to an empty tank. Pump X fills the tank with water at a constant rate, while pump Y drains water out of the tank at a constant rate. The two pumps finish filling the tank in three times the duration it would take pump X alone to fill the tank. If pump Y alone can empty a whole tank in 36 minutes, then how many minutes does it take pump X alone to fill the tank?