Correct. Since $\displaystyle{V}={{s}}^{{2}}{h}\usepackage{cmbright}\Huge\$ , you know that $\displaystyle{4500}={{s}}^{{2}}{\left({20}\right)}\usepackage{cmbright}\Huge\$ , so $\displaystyle{{s}}^{{2}}=\frac{{4500}}{{20}}={225}\usepackage{cmbright}\Huge\$ . Therefore, $\displaystyle{s}=\sqrt{{225}}={15}\usepackage{cmbright}\Huge\$ .