Exer. 6.1
Exer. 6.2
Exer. 6.2, another answer
Exer. 6.2, still another answer
Exer. 6.3
Exer. 6.4
Exer. 6.4, another solution
Exer. 6.5
Exer. 6.6
Exer. 6.7
Exer. 6.8
Exer. 6.9
Exer. 6.10