Preparing for their dates on a Friday night, it takes each girl (approximately) a normally distributed amount of time to prepare, with an average of 40 minutes (per girl) to get ready, and a standard deviation of 15 minutes. The 50 men who are waiting for them in the lobby are mostly science majors, and they start to wonder: What is the probability that the average waiting time exceeds 36 minutes (where the average is taken over the 50 preparation times of the women)?