Give a quick stream of consciousness before answering the following question. A train 540 meters long is running with a speed of 54 kmph. The time taken by it to cross a tunnel 180 meters long is?
Options:
(A) 18 sec
(B) 28 sec
(C) 48 sec
(D) 29 sec
(E) 24 sec

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.
user
D = 540 + 180 = 720
S = 54 * 5/18 = 15 mps
T = 720/15 = 48 se
The answer: (C).