Exer. 11.1 There are 2 solutions here
Exer. 11.2
Exer. 11.3
Exer. 11.4
Exer. 11.5
Exer. 11.6
Exer. 11.7
Exer. 11.8
Exer. 11.9
Exer. 11.10
Exer. 11.11
Exer. 11.12
Exer. 11.13
Exer. 11.14