7.1 problem Exercise 20.1, page 220
  7.2 problem Exercise 20.2, page 220
  7.3 problem Exercise 20.3, page 220
  7.4 problem Exercise 20.5, page 220
  7.5 problem Exercise 20.6, page 220
  7.6 problem Exercise 20.7, page 220
  7.7 problem Exercise 20.8, page 220
  7.8 problem Exercise 20.9, page 220
  7.9 problem Exercise 20.10, page 220
  7.10 problem Exercise 20.11, page 220
  7.11 problem Exercise 20.12, page 220
  7.12 problem Exercise 20.13, page 220
  7.13 problem Exercise 20.14, page 220
  7.14 problem Exercise 20.15, page 220
  7.15 problem Exercise 20.16, page 220
  7.16 problem Exercise 20.17, page 220
  7.17 problem Exercise 20.18, page 220
  7.18 problem Exercise 20.19, page 220
  7.19 problem Exercise 20.20, page 220
  7.20 problem Exercise 20.21, page 220
  7.21 problem Exercise 20.22, page 220
  7.22 problem Exercise 20.23, page 220
  7.23 problem Exercise 20.24, page 220
  7.24 problem Exercise 20.25, page 220
  7.25 problem Exercise 20.26, page 220
  7.26 problem Exercise 20.27, page 220
  7.27 problem Exercise 20.28, page 220
  7.28 problem Exercise 20.29, page 220
  7.29 problem Exercise 20.30, page 220
  7.30 problem Exercise 20, problem 31, page 220
  7.31 problem Exercise 20, problem 32, page 220
  7.32 problem Exercise 20, problem 33, page 220
  7.33 problem Exercise 20, problem 34, page 220
  7.34 problem Exercise 20, problem 35, page 220