# Frustums of sphere

Geometry Level pending

You are given a frustum of a sphere with height of 4 cm, upper base radius of 2 cm, and lower base radius of 3 cm.. If the square of the radius of the sphere can be expressed in the form of $$\frac ab$$ for coprime positive integers $$a$$ and $$b$$, find the value of $$a-b$$.

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