Word Nerd

I have a really bad stats teacher and I'm really struggling to understand the work in his class. Can anyone help with this question? 20,000 men attend NDU, a university whose athletic mascot is the leprechaun. The mascot requirements demand a person no taller than five feet. If the mean height of men is 5'8" with a standard deviation of 2.5", and the student body forms a normal distribution for height, a) how many potential leprechauns are there in the student body? b) how many men are as tall or taller than 6'5"? I don't just want an answer. I want to know how to get to the answer. If anyone can help that would be great.