Chapter 5.6, Problem 13P

In each of Problems $1$ through $13$, find the solutions of the given initial value problem. Draw the graphs of the solution and of the forcing function; explain how they are related.

$y^{(4)}+5y\text{'}\text{'}+4y=1-u_{\pi }(t);$ $y(0)=0,$

$y\text{'}(0)=0;$ $y\text{'}\text{'}(0)=0$,      $y\text{'}\text{'}\text{'}(0)=0$