Machine A and machine B process the same work at different rates. Machine C processes work as fast as Machines A and B combined. Machine D processes work three times as fast as Machine C; Machine D’s work rate is also exactly four times Machine B’s rate. Assume all four machines work at fixed unchanging rates. If Machine A works alone on a job, it takes 7 hours and 20 minutes. If all four machines work together on the same job simultaneously, how many minutes will it take all of them to complete it?	Select
A) 20
B) 22
C) 24
D) 26
E) 28
C = A + B   D = 3C = 3(A+B) = 4B   Then B = 3A and C = 4A   The combined rate of the four machines is A + 3A + 4A + 12A = 20A   Machine A can complete the work in 440 minutes, so its rate is 1/440 of the work per minute.   The combined rate is 20/440 = 1/22 so the work will be completed in 22 minutes.   The answer is 22.
<result>B</result>
Machine A and machine B process the same work at different rates. Machine C processes work as fast as Machines A and B combined. Machine D processes work three times as fast as Machine C; Machine D’s work rate is also exactly four times Machine B’s rate. Assume all four machines work at fixed unchanging rates. If Machine A works alone on a job, it takes 7 hours and 20 minutes. If all four machines work together on the same job simultaneously, how many minutes will it take all of them to complete it?