Excluding stoppages, the speed of a train is 42 kmph and including stoppages it is 36 kmph. Of how many minutes does the train stop per hour?
Choose the correct choice from the following:
A) 7.5 B) 8.5 C) 9.5 D) 4.5 E) 6.5

Rationale: t = 6 / 42 * 60 = 8.5 answer : b
Answer: B