4.1 problem 19 (a)
4.2 problem 19 (c)
4.3 problem 19 (d)
4.4 problem 19 (e)
4.5 problem 19 (f)
4.6 problem 19 (g)
4.7 problem 19 (h)
4.8 problem 19 (i)
4.9 problem 19 (j)
4.10 problem 19 (k)
4.11 problem 19 (L)
4.12 problem 19 (m)
4.13 problem 19 (o)
4.14 problem 19 (p)
4.15 problem 19 (q)
4.16 problem 19 (r)
4.17 problem 19 (s)
4.18 problem 19 (t)
4.19 problem 22 (a)
4.20 problem 22 (b)
4.21 problem 23 (a)
4.22 problem 23 (b)
4.23 problem 23 (c)
4.24 problem 23 (d)
4.25 problem 23 (e)