Excluding stoppages, the speed of a train is 54 kmph and including stoppages it is 36 kmph. Of how many minutes does the train stop per hour?
Pick one:
A) 20 B) 17 C) 15 D) 18 E) 12

Rationale: "t = 18 / 54 * 60 = 20 answer : a"
Answer: A