A Zener of breakdown voltage $\mathrm{V}_{\mathrm{Z}}=8 \mathrm{~V}$ and maximum zener current, $\mathrm{I}_{\mathrm{ZM}}=10 \mathrm{~mA}$ is subjected to an input voltage $\mathrm{V}_{\mathrm{i}}=10 \mathrm{~V}$ with series resistance $\mathrm{R}=100 \Omega$. In the given circuit $\mathrm{R}_{\mathrm{L}}$ represents the variable load resistance. The ratio of maximum and minimum value of $R_L$ is $\_\_\_\_$