AMC 10B 2025 (Problem 5)

\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

\text{(A)}\;20

\text{(B)}\;30

\text{(C)}\;40

\text{(D)}\;50

\text{(E)}\;60