Working alone, pump A can empty a pool in 6 hours. Working alone, pump B can empty the same pool in 9 hours. Working together, how many minutes will it take pump A and pump B to empty the pool?  Choose the most appropriate option:	A) 192	B) 200	C) 208	D) 216	E) 224

Rationale: "pump a can empty ( 1 / 6 ) of the pool per hour . pump b can empty ( 1 / 9 ) of the pool per hour . together the pumps can empty 1 / 6 + 1 / 9 = 5 / 18 of the pool per hour . 1 pool / ( 5 / 18 ) pool per hour = 18 / 5 hours = 216 minutes . the answer is d ."
Answer: D