Volume of Sphere is V=(4/3)*PI*r^3
The radius of the volleyball is 13 inches
So V=(4/3) * 3.14 * 13^3 = 9198 cubic inches
Volume of a cylinder is V=pi * r^2 *h
Since they say the ball fits perfectly
The radius is 13 and the height is 26 ( the diameter of the ball)
So V=3.14 * 13^2 * 26 = 13,797 cubic inches
13797 – 9198 = 4,599 cubic inches of empty space
I really hope this helps.