AMC 8 1993 Problem 18

The rectangle shown has length $AC=32$, width $AE=20$, and $B$ and $F$ are midpoints of $\overline{AC}$ and $\overline{AE}$, respectively. The area of quadrilateral $ABDF$ is

$\text{(A)}\ 320 \text{(B)}\ 325 \text{(C)}\ 330 \text{(D)}\ 335 \text{(E)}\ 340$