Nine carpenters can individually complete a particular task in 3, 4, 5, and 7 hours, respectively. What is the maximum fraction of the task that can be completed in forty-five minutes if eight of the carpenters work together at their respective rates ?  Choose the correct choice.
A) 11/15
B) 3/5
C) 11/30
D) 47/135
E) 5/9
Farmer A, B, C, and D   A's rate: 1/3 job/hour   B's rate: 1/4 job/hour   C's rate: 1/5 job/hour   D's rate: 1/7 job/hour   By intuition we know that the three fastest farmers are A B and C.   As such   (1/3 + 1/4 + 1/5)*(8/9) = ?   47/135 or (47/135)
<result>D</result>
Nine carpenters can individually complete a particular task in 3, 4, 5, and 7 hours, respectively. What is the maximum fraction of the task that can be completed in forty-five minutes if eight of the carpenters work together at their respective rates ?