2.4.3, due on September 12

The Euler Phi function idea was a bit confusing to me, but I think that is mainly because I've only read it and this book isn't the best at explaining things. So I expect I'll understand a lot better once I've heard it explained as well. I think that will make it a lot more concrete. I still loving getting to relearn things we did in 371 because it makes them so much more solid in my mind to see them looking from the perspective of already having a fairly good grasp on them.