Correct. The formula for the volume of a cube is $\displaystyle{V}={{a}}^{{3}}\usepackage{cmbright}\Huge\$ , where $\displaystyle{a}=\usepackage{cmbright}\Huge\$ side length. Substitute $\displaystyle{a}={4}\usepackage{cmbright}\Huge\$ into the formula:

$\displaystyle{V}={{a}}^{{3}}\usepackage{cmbright}\Huge\$

$\displaystyle{V}={{4}}^{{3}}\usepackage{cmbright}\Huge\$

$\displaystyle{V}={64}\usepackage{cmbright}\Huge\$ cubic feet