Excluding stoppages, the speed of a train is 50 kmph and including stoppages it is 30 kmph. Of how many minutes does the train stop per hour?	Choose the correct option:
A) 82	B) 17	C) 12	D) 24	E) 18

Rationale: "explanation : t = 20 / 50 * 60 = 24 answer : option d"
Answer: D