Working alone, pump A can empty a pool in 4 hours. Working alone, pump B can empty the same pool in 6 hours. Working together, how many minutes will it take pump A and pump B to empty the pool?
Choose the correct choice from the following answers.
A) 132	B) 138	C) 144	D) 150	E) 156
Pump A can empty (1/4) of the pool per hour.   Pump B can empty (1/6) of the pool per hour.   Together the pumps can empty 1/4+1/6=5/12 of the pool per hour.   1 pool / (5/12) pool per hour = 12/5 hours = 144 minutes.   The answer is 144.
<result>C</result>
Working alone, pump A can empty a pool in 4 hours. Working alone, pump B can empty the same pool in 6 hours. Working together, how many minutes will it take pump A and pump B to empty the pool?