9.5. Two spheres touch the plane of triangle $A B C$ at points $A$ and $B$ and are located on opposite sides of this plane. The sum of the radii of these spheres is 11, and the distance between their centers is $\sqrt{481}$. The center of a third sphere with radius 9 is at point $C$, and it touches each of the two first spheres externally. Find the radius of the circle circumscribed around triangle $A B C$.
Answer. $3 \sqrt{10} \approx 9.49$.