Question 21Triangles $ABC$ and $ABD$ are isosceles with $AB=AC=BD,$ and $\overline{BD}$ intersects $\overline{AC}$ at $E.$ If $\overline{BD}\perp\overline{AC},$ then $\angle C+\angle D$ is $115^\circ$$120^\circ$$130^\circ$$135^\circ$not uniquely determined
