Applied exercises

1/13 Exercise 13.11

1/13 Exercise 13.12

1/13 Exercise 13.13

1/13 Exercise 13.14

1/13 Exercise 13.15

1/13 Exercise 13.16

1/13 Exercise 13.17

1/13 Exercise 13.18

1/13 Exercise 13.19

1/13 Exercise 13.20

1/13 Exercise 13.21