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

Ex Input:
Problem: excluding stoppages , the average speed of a bus is 60 km / hr and including stoppages , the average speed of the bus is 40 km / hr . for how many minutes does the bus stop per hour ?

Ex Output:
20 min

Ex Input:
Problem: the average salary of 20 people in the shipping department at a certain firm is $ 1000 . the salary of 10 of the employees is $ 600 each and the salary of 6 of the employees is $ 200 each . what is the average salary of the remaining employees ?

Ex Output:
$ 3200

Ex Input:
Problem: how many integerskgreater than 100 and less than 700 are there such that if the hundreds and the units digits ofkare reversed , the resulting integer is k + 99 ?

Ex Output:
50