Suppose that on a particular day two persons A and B arrive at a certain store independently of each other. Suppose that A remains in the store for 15 minutes and B remains in the store for 10 minutes. If the time of arrival of each person has a uniform distribution over the hour between 9:00 A.M. and 10:00 A.M., what is the probability that A and B will be in the store at the same time?