Excluding stoppages, the speed of a bus is 40 kmph and including stoppages, it is 30 kmph. For how many minutes does the bus stop per hour?	Choose the correct choice from the following answers:
A) 10 min
B) 12 min
C) 18 min
D) 15 min
E) 20 min
Due to stoppages, it covers 10 km less.   Time taken to cover 10 km = (10/40 x 60) min = 15 min   Answer : 15 min
<result>D</result>
Excluding stoppages, the speed of a bus is 40 kmph and including stoppages, it is 30 kmph. For how many minutes does the bus stop per hour?