Question 24
Trapezoid $ABCD$ has parallel sides $AB$ and $CD$, with $BC$ perpendicular to them. Suppose $AB=13$, $BC=16$ and $DC=11$. Let $E$ be the midpoint of $AD$ and $F$ the point on $BC$ so that $EF$ is perpendicular to $AD$. Find the area of quadrilateral $AEFB$.
