We wish to separate a mixture of \(40.0 \mathrm{~mol} \%\) benzene and \(60.0 \mathrm{~mol} \%\) ethylene dichloride in a distillation column with a partial reboiler and a total condenser. The feed rate is \(750 \mathrm{~mol} / \mathrm{h}\), and the feed is a saturated vapor. We desire a distillate product of \(99.2 \mathrm{~mol} \%\) benzene and a bottoms product that is \(0.5 \mathrm{~mol} \%\) benzene. Reflux is a saturated liquid, and CMO can be used. Equilibrium data can be approximated with an average relative volatility of 1.11 (benzene is more volatile).

a. Find the minimum external reflux ratio.

b. Use the Fenske equation to find the number of stages required at total reflux.

c. Estimate the total number of stages required for this separation using the Gilliland correlation for \(\mathrm{L} / \mathrm{D}=1.2(\mathrm{~L} / \mathrm{D})_{\min }\).