Explanation
From the image, we can see that the radius of the cylinder is given as
[tex]\frac{d}{2}=\frac{20}{2}=10ft[/tex]The height of the cylinder is 40ft. Therefore, the volume of the cylinder is
[tex]volume=\pi r^2h=3.14\times10^2\times40=12560[/tex]Answer: 12560 cubic feet