Correct. This problem tells you that $\displaystyle{N}=\frac{{k}}{{C}}\usepackage{cmbright}\Huge\$ , for some constant k. Substituting the given information gives you $\displaystyle{9}=\frac{{k}}{{8}}\usepackage{cmbright}\Huge\$ , so $\displaystyle{k}={72}\usepackage{cmbright}\Huge\$ . If $\displaystyle{C}={12}\usepackage{cmbright}\Huge\$ , then this gives you: $\displaystyle{N}=\frac{{72}}{{12}}\usepackage{cmbright}\Huge\$

Therefore, $\displaystyle{N}={6}\usepackage{cmbright}\Huge\$ .