AMC 12 2007b Problem 7

All sides of the convex pentagon $ABCDE$ are of equal length, and $\angle A = \angle B = 90^{\circ}$. What is the degree measure of $\angle E$?

$\mathrm {(A)} 90 \mathrm {(B)} 108 \mathrm {(C)} 120 \mathrm {(D)} 144 \mathrm {(E)} 150$