In Exercises 19-28 use Theorem 8.4.2 to express the inverse transforms in terms of step functions, and then find distinct formulas the for inverse transforms on the appropriate intervals, as in Example 8.4.7. Where indicated by C/G, graph the inverse transform. 19. H(s)= e-2s 5-2 20. H(s) = e-s s(s+1) 21. C/G H(s)= = e-s 22. C/G H(s)= + +e-s +e-3s S