Laplace II: Steps, Impulses & Convolution · Medium problem

A motor's control signal is $f(t)=2$ for $0\le t<1$, $f(t)=-1$ for $1\le t<3$, and $f(t)=0$ for $t\ge3$. Write $f$ with unit steps and find $\mathcal{L}\{f\}(\ln 2)$. Give an exact answer.