The volume of a cone is such that [tex]V= \frac{1}{3} \pi r^2h[/tex], where r is the radius and h is the height.
Recall that the diameter is twice the radius. So given that the diameter is 8 ft, the radius must be 4 ft. The height is given as 5 ft.
Plugging into the formula, you have [tex]V= \frac{1}{3}(3.14)(4)^2(5) = 83.73 \ ft^3[/tex]
