Question 25
Points $A$, $B$, $C$ lie on a circle $\omega$ such that $BC$ is a diameter. $AB$ is extended past $B$ to point $B'$, and $AC$ is extended past $C$ to point $C'$ such that line $B'C'$ is parallel to $BC$ and tangent to $\omega$ at point $D$. If $B'D = 4$ and $C'D = 6$, compute $BC$.
