  Let $V$ be a bounded domain with smooth boundary in $\R^n$, and $D^*V$ denote
its disc cotangent bundle. We compute symplectic homology of $D^*V$, in terms
of relative homology of loop spaces on the closure of $V$. We use this result
to show that Floer-Hofer capacity of $D^*V$ is between $2r(V)$ and
$2(n+1)r(V)$, where $r(V)$ denotes inradius of $V$. As an application, we study
periodic billiard trajectories on $V$.
