Let $ABCD$ be an isosceles trapezoid with $\overline{BC} \parallel \overline{AD}$ and $AB=CD$. Points $X$ and $Y$ lie on diagonal $\overline{AC}$ with $X$ between $A$ and $Y$, as shown in the figure. Suppose $\angle AXD = \angle BYC = 90^\circ$, $AX = 3$, $XY = 1$, and $YC = 2$. What is the area of $ABCD$?

$\textbf{(A)}\: 15\qquad$ $\textbf{(B)} \: 5\sqrt{11}\qquad$ $\textbf{(C)} \: 3\sqrt{35}\qquad$ $\textbf{(D)} \: 18\qquad$ $\textbf{(E)} \: 7\sqrt{7}$