Machine A can finish a job in 4 hours, Machine В can finish the job in 3 hours, and Machine С can finish the job in 6 hours. How many hours will it take for A, B, and С together to finish the job?	Pick:
A) 3 / 2	B) 4 / 3	C) 5 / 4	D) 6 / 5	E) 8 / 7

Rationale: "the combined rate is 1 / 4 + 1 / 3 + 1 / 6 = 9 / 12 of the job per hour . the time to complete the job is 12 / 9 = 4 / 3 hours . the answer is b ."
Answer: B