Question 138159
First, you want to find the diameter, D, of the rubber ball when you know its circumference, C.
{{{C = (pi)D}}} 
{{{D = C/(pi)}}} Substitute C = 13 and {{{(pi) = 3.14}}}
{{{D = 13/3.14}}}
{{{D = 4.14}}}
So, to accomodate the ball whose diameter is a little over 4 inches, you will need a box (cube) whose side measures over 4 inches.
The best choice is the box whose side is 5 inches.