I need typed answer don't write in a paper plz

Bus A and B arrive at a station at random between 9:00 AM and 9:20 AM. Bus A stops for 4 minutes and the Bus B stops for 5 minutes assuming that the buses arrive independently of each other. Find

1) the probability that two buses are both at the station (they could enter the station at different time)

2) The probability that Bus A arrives before Bus B, and B arrives before A.

explain maths???