Two friends, Alicia and Joe, agreed to met at 8 o'clok to go to the movies. As they're never on time, it can be suppose that the times in which each of them arrives at the meeting point are independent random variables X and Y , both with uniform distribution between 8 and 9 o'clock. If they are willing to wait no more than 10 minutes to each other from the moment they arrive, what's the probability that they don't meet?.