Given the rationale, provide a reasonable question and answer. Step-by-step reasoning process: The time they take will be what the 1st friend takes to complete one circumference as he is the slowest and that is the point all 3 of them will be together at the end of 7 mins.
 The question and answer:
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Three friends-whose walking rates are 1 ft./sec., 3ft./sec.,and 6ft./sec. start together walking in the same direction around a circular track that is 420 feet in circumference.After how many minutes are the three of them together again?
Options:
(A) 5 mins
(B) 10 mins
(C) 15 mins
(D) 3 mins
(E) 7 mins
The answer is (E)
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