Excluding stoppages, the speed of a train is 45 kmph and including stoppages it is 30 kmph. Of how many minutes does the train stop per hour?  Answers.
A) 5 B) 10 C) 20 D) 30 E) 40

Rationale: "explanation : t = 15 / 45 * 60 = 20 answer : option c"
Answer: C