9.1 problem 1
  9.2 problem 2
  9.3 problem 3
  9.4 problem 4
  9.5 problem 5
  9.6 problem 6
  9.7 problem 7
  9.8 problem 8
  9.9 problem 9
  9.10 problem 10
  9.11 problem 11
  9.12 problem 12
  9.13 problem 13
  9.14 problem 14
  9.15 problem 15
  9.16 problem 16
  9.17 problem 23
  9.18 problem 24
  9.19 problem 25
  9.20 problem 26
  9.21 problem 27
  9.22 problem 28
  9.23 problem 29
  9.24 problem 30
  9.25 problem 40
  9.26 problem 41
  9.27 problem 42
  9.28 problem 43
  9.29 problem 44
  9.30 problem 45