In $\triangle ABC$, $AB=10$, $AC=18$, and $\angle B=130^\circ.$ Let $O$ be the center of the circle containing $A$, $B$, and $C.$ What is the degree measure of $\angle CAO$? $\textbf{(A)}~20 \qquad$ $ \textbf{(B)}~30 \qquad$ $ \textbf{(C)}~40 \qquad$ $ \textbf{(D)}~50 \qquad$ $ \textbf{(E)}~60$