ch05 initial commit
ex 5.1, ex 5.2
ex 5.3
ex 5.4,5.5,5.6
ex 5.7
ex 5.7 revised
ex 5.8
stopping for today (ex 5.9)
ex 5.12
ex 5.13
ex 5.13 finished
ex 5.14, 5.15
ex 5.16 (Books solution)