388. Three Napkins. One lady made 3 round napkins with radii of 2, 3, and 10 inches, respectively. She placed them on a round table so that each napkin touched the other two and the edge of the table. What is the radius of the table top?
388. If the centers of napkins with radii of 2, 3, and 10 inches are located at points \( C, A \), and \( B \) respectively, then these points form the vertices of a right triangle with sides 5, 12, and 13 inches. Completing the figure \( ABC \) to a rectangle, we denote its fourth vertex as \( O \). From point \( O \), draw lines through points \( B, C \), and \( A \), intersecting the given circles at points \( P, Q \), and \( R \) respectively. Then \( OP = OQ = OR = 15 \) inches. This is the desired radius. [For a more general solution, see Scripta Mathematica 21, 46-47 (1955)].

[U. Howard, M. M., 41, 295 (May 1968).]