21-1

21-2

21-3

21-4

21-5
1 Solutions

21-6
1 Solutions

21-7

21-8

21-9

21-10
1 Solutions

21-11
3 Solutions

21-12
1 Solutions

21-13
1 Solutions

21-14
2 Solutions

21-15
4 Solutions

21-16
1 Solutions

21-17

21-18

21-19

21-20
2 Solutions

22-1
3 Solutions

22-2
1 Solutions

22-3
1 Solutions

22-4
1 Solutions

22-5
4 Solutions

22-6
2 Solutions

22-7
2 Solutions

22-8
1 Solutions

22-9
1 Solutions

22-10
1 Solutions

22-11
2 Solutions

22-12
1 Solutions

22-13
3 Solutions

22-14
1 Solutions

22-15
3 Solutions

22-16
1 Solutions

22-17

22-18
1 Solutions

22-19

22-20