well, first off let's see what's the volume or namely the cubic foot capacity of one tank.
[tex]\textit{volume of a cylinder}\\\\ V=\pi r^2 h~~ \begin{cases} r=radius\\ h=height\\[-0.5em] \hrulefill\\ r=7\\ h=2 \end{cases}\implies \begin{array}{llll} V=\pi (7)^2(2)\implies V=98\pi \\\\ \stackrel{\textit{cost for one tank}~\hfill }{3(98\pi )\implies 3(98)(3.14)\implies \stackrel{\$}{923.16}} \end{array}[/tex]
