4.1 problem Problem 3.1
  4.2 problem Problem 3.2
  4.3 problem Problem 3.3
  4.4 problem Problem 3.4
  4.5 problem Problem 3.6
  4.6 problem Problem 3.7
  4.7 problem Problem 3.8
  4.8 problem Problem 3.11
  4.9 problem Problem 3.12
  4.10 problem Problem 3.14
  4.11 problem Problem 3.18
  4.12 problem Problem 3.19
  4.13 problem Problem 3.20
  4.14 problem Problem 3.21
  4.15 problem Problem 3.22
  4.16 problem Problem 3.23
  4.17 problem Problem 3.24
  4.18 problem Problem 3.31
  4.19 problem Problem 3.32
  4.20 problem Problem 3.33
  4.21 problem Problem 3.34
  4.22 problem Problem 3.35
  4.23 problem Problem 3.38