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