First find the volume of the cylinder:

$\displaystyle{V}=\pi{{r}}^{{2}}{h}=\pi{{\left({10}\right)}}^{{2}}\cdot{15}\approx{3.14}\cdot{1500}={4},{710}\usepackage{cmbright}\Huge\$

Then find the volume of the hole shaped like a rectangular prism:

$\displaystyle{V}={l}\cdot{w}\cdot{h}={5}\cdot{3}\cdot{15}={225}\usepackage{cmbright}\Huge\$

Subtract the volume of the hole from the volume of the cylinder: $\displaystyle{4},{710}-{225}={4},{485}\usepackage{cmbright}\Huge\$

The volume of the solid is 4,485 cubic feet.