2.82, 2.83, 2.84 finished.

2.82 took a lot of time, and I still needed to reference others work. It
turned out that we completely gutted apply-generic in 2.84 anyway and
took a different approach for handling data in the arithmetic package
system. It was all very interesting.

Here's to pushing on in the book, and not being stuck for two weeks on a
problem again!