5.1 problem 4
 5.2 problem 5
 5.3 problem 6
 5.4 problem 7
 5.5 problem 8
 5.6 problem 9
 5.7 problem 10
 5.8 problem 11
 5.9 problem 12
 5.10 problem 13
 5.11 problem 14
 5.12 problem 15
 5.13 problem 16
 5.14 problem 17
 5.15 problem 19