Section 18.2: 21, 24
Section 18.3: 20
Section 18.4: 24.
Section 18.2: 2, 5, 8, 10, 13, 16, 20. Section 18.3: 1, 4, 8, 12, 13, 16, 20, 24. Section 18.4: 1, 4, 7, 12, 15, 18, 20, 23. Section 19.1: 2, 4, 8, 10, 12, 16, 19, 22, 27, 30.