Excluding stoppages, the speed of a bus is 54 km/hr and including stoppages, it is 45 km/hr. For how many minutes does the bus stop per hour?  Select.
A) 22
B) 10
C) 99
D) 77
E) 29

Rationale: "due to stoppages , it covers 9 km less . time taken to cover 9 km = 9 / 54 * 60 = 10 min . answer : b"
Answer: B