The task is to generate the correct answer for a given math problem.

Q: Problem: excluding stoppages , the average speed of a bus is 60 km / hr and including stoppages , the average speed of the bus is 15 km / hr . for how many minutes does the bus stop per hour ?

A: 4
****
Q: Problem: what is the probability of getting a queen or spade from a set of cards ?

A: 4 / 13
****
Q: Problem: what is the prime factors ’ number of 12 ?

A:
3
****