3.3, due on September 19

1. I had a harder time understanding a homomorphism than an isomorphism.  It still feels like just an abstract property to me rather than a description of the function.  Isomorphism makes much more sense; it's a way to tell if two rings are essentially the same.

2. We have been learning about isomorphic vector spaces in one of the ACME classes (Math 344), so the concept of an isomorphism is vary familiar.  For rings, however, there are many more nice properties than we covered for vector spaces, such as the fact that isomorphisms preserve commutativity and units.