AMC 8 2007 Problem 8

In trapezoid $ABCD$, $\overline{AD}$ is perpendicular to $\overline{DC}$, $AD = AB = 3$, and $DC = 6$. In addition, $E$ is on $\overline{DC}$, and $\overline{BE}$ is parallel to $\overline{AD}$. Find the area of $\triangle BEC$.

$\textbf{(A)}\ 3 \textbf{(B)}\ 4.5 \textbf{(C)}\ 6 \textbf{(D)}\ 9 \textbf{(E)}\ 18$