Seven 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 six of the carpenters work together at their respective rates ?  Select the correct option.
A) 11/15	B) 3/5	C) 11/30	D) 47/70	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)*(6/7) = ?   47/70 or (47/70)
<result>D</result>
Seven 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 six of the carpenters work together at their respective rates ?