Correct. To find the area, you substitute in $\displaystyle\frac{{{5}{x}{y}}}{{z}}\usepackage{cmbright}\Huge\$ for the radius, resulting in $\displaystyle\pi{{\left(\frac{{{5}{x}{y}}}{{z}}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ . You can simplify this expression to $\displaystyle\frac{{{25}\pi{{x}}^{{2}}{{y}}^{{2}}}}{{{{z}}^{{2}}}}\usepackage{cmbright}\Huge\$ .