The volume of a sphere of radius $r$ is $\displaystyle V = \frac{4}{3} \pi r^3$.

(a) Write a differential formula that estimates the change in volume of a sphere when the radius changes from $r_0$ to $r_0 + dr$. Enter $r_0$ as r0 and $dr$ as dr.
$dV$ = help (formulas)

(b) Write a differential formula that estimates the change in volume of a sphere when the radius changes from $7$ to $7 + dr$.
$dV$ = help (formulas)

(c) Use a differential to estimate the change in volume of a melting spherical snowball when the radius changes from $7 \ \mathrm{cm}$ to $6.6 \ \mathrm{cm}$.
$dV$ = $\mathrm{cm^3}$