13.1 problem 20.1 (a)
13.2 problem 20.1 (b)
13.3 problem 20.1 (c)
13.4 problem 20.1 (d)
13.5 problem 20.1 (e)
13.6 problem 20.1 (f)
13.7 problem 20.1 (g)
13.8 problem 20.1 (h)
13.9 problem 20.1 (i)
13.10 problem 20.1 (j)
13.11 problem 20.1 (k)
13.12 problem 20.1 (L)
13.13 problem 20.1 (m)
13.14 problem 20.1 (n)
13.15 problem 20.1 (o)
13.16 problem 20.1 (p)
13.17 problem 20.1 (q)
13.18 problem 20.1 (r)
13.19 problem 20.2 (a)
13.20 problem 20.2 (b)
13.21 problem 20.2 (c)
13.22 problem 20.2 (d)
13.23 problem 20.2 (e)
13.24 problem 20.2 (f)
13.25 problem 20.4 (a)
13.26 problem 20.4 (b)
13.27 problem 20.4 (c)
13.28 problem 20.4 (d)
13.29 problem 20.4 (e)
13.30 problem 20.4 (f)
13.31 problem 20.4 (g)
13.32 problem 20.4 (h)