6.3

1. This really wasn't that difficult of a section. I like the idea of maximals.

2. An integral domain is related to Z mod p where p is prime. Let ~ be congruence. If ab ~ 0 (mod n), with a, b both nonzero, then n must be composite since ab is a multiple of n (assuming n divides neither a nor b). Actually, typing this out, this isn't really a new concept. So I guess I'm making the connection now that I should have made before.