Let $\mathrm{A}, \mathrm{B}$ and C be three points on the parabola $y^2=6 x$ and let the line segment $A B$ meet the line $L$ through C parallel to the x -axis at the point D . Let M and N respectively be the feet of the perpendiculars from A and B on L . Then $\left(\frac{A M \cdot B N}{C D}\right)^2$ is equal to $\_\_\_\_$ .