Answer :
Check the picture below.
[tex]\textit{volume of a pyramid}\\\\ V=\cfrac{Bh}{3}~~ \begin{cases} B=\stackrel{base}{area}\\ h=height\\[-0.5em] \hrulefill\\ B=12.4\\ h=5 \end{cases}\implies V=\cfrac{(12.4)(5)}{3}\implies V=20.\overline{6}~ft^3[/tex]
