Who are talking in this dialogue?

W: Oh, I’m glad to see you, Harry. You took Introduction to Science last year, didn’t you?
M: I sure did.
W: Well, I’m thinking about taking it next year.
M: Don’t do it.
W: Why not? Is the professor awful?
M: The professor is nice enough, but the course is nothing but physics and chemistry with lots of equations. You can’t just mix the right chemicals and watch what happens. As you go along you have to keep careful notes and turn it all into a bunch of numbers and formulas after an experiment is over. It was the worst course I’ve ever taken.
W: I like numbers and formulas.
M: Well, you’ll love these, but all I was interested in was biology, and we didn’t get to that till the last three weeks of class. What a year!