The notation V(r) actually gives the volume of air inside the basketball. V(r) is volume as a function of radius, r It can be written as: V(r) = 4/3πr³ So, for any value of r, we can get the volume V. For, example, when r = 7cm we can say; V(7) = 4/3 x 22/7 x 7³ = 1437.33 cm³