Machine A can finish a job in 4 hours, Machine В can finish the job in 2 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?
Choose the correct choice:
A) 4/3  B) 6/5  C) 8/7  D) 10/9  E) 12/11
The combined rate is 1/4+1/2+1/6 = 11/12 of the job per hour.   The time to complete the job is 12/11 hours.   The answer is 12/11.
<result>E</result>
Machine A can finish a job in 4 hours, Machine В can finish the job in 2 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?