A Spherical Balloon with Radius $r$ Inches Has Volume $$\frac { 4 } { 3 } \pi r ^ { 3 } \text {. }$$

Short Answer

A spherical balloon with radius $r$ inches has volume
$$\frac { 4 } { 3 } \pi r ^ { 3 } \text {. }$$
Find a function that represents the amount of air required to inflate the balloon from a radius of $r$ inches to a radius of $r + 1$ inches.