I need help figuring with a Normal Deviate Z Test below.

8.The average height of U.S. adult males is 69.5 in. and the standard deviation is 2.0. A physician thinks that this national mean seems a little short for his patients, so he records the height of the next 100 adult males to visit his office. Their average height is 69.75 in. If this physician's adult male patients are just a representative sample of nationwide adult males, what is the probability that his patients were so tall?