19 Chapter 4, Linear Systems. Exercises page 202

 19.1 problem 1(a)
 19.2 problem 1(b)
 19.3 problem 1(c)
 19.4 problem 1(d)
 19.5 problem 1(e)
 19.6 problem 1(f)
 19.7 problem 3(a)
 19.8 problem 3(b)