jmc

The area of the quadrilateral $ABDF$ is equal to the areas of the two right triangles $△BCD$ and $△EFD$ subtracted from the area of the rectangle $ABCD$. Because $B$ and $F$ are midpoints, we know the dimensions of the two right triangles. $$(20)(32)-\frac{(16)(20)}{2}-\frac{(10)(32)}{2}=640-160-160=\boxed{320}$$