Exercise 23.1.1
Exercise 23.2.1 and 23.2.2
Exercise 23.2.3
Exercise 23.2.4
Exercise 23.2.5
Exercise 23.3.1
Exercise 23.3.2
Exercise 23.3.4
Exercise 23.3.5
Exercise 23.3.6
Exercise 23.3.7
Exercise 23.3.8
Exercise 23.3.9
Add a TODO
Exercise 24.0.7
Exercise 24.0.8
Exercise 24.0.9
Exercise 25.1.1
Exercise 25.1.2
Exercise 25.2.2