S = 180/6 * 18/5 = 108 kmphis the reasoning for what question and answer pair?

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Q: A 180 meter long train crosses a man standing on the platform in 6 sec. What is the speed of the train?
Options:
(A) 48 kmph
(B) 52 kmph
(C) 108 kmph
(D) 100 kmph
(E) 98 kmph
A: (C)