015 Review Problem - Volume of spherical shell

$R = \frac{1}{2}(12) = 6 ~ \text{in.}$

$r = R - 2 = 4 ~ \text{in.}$
 

$V = \frac{4}{3}\pi (R^3 - r^3)$

$V = \frac{4}{3}\pi (6^3 - 4^3)$

$V = \frac{608}{3}\pi ~ \text{in.}^3$

$V = 636.70 ~ \text{in.}^3$           answer