$16.*$ We are separating a mixture of ethanol and n$-$propanol. Ethanol is more volatile and the relative volatility is approximately constant at $2\mathrm{.}10.$ The feed flow rate is $1000$kmo$\frac{l}{h}.$ Feed is $60$mol$\%$ ethanol and is a saturated vapor. We desire $x_D=0\mathrm{.}99$ mole fraction ethanol and $x_B=0\mathrm{.}008$ mole fraction ethanol. Reflux is a saturated liquid.

There are $30$ stages in the column, Use the Fenske$-$Underwood$-$Gilliland approach to determine

a$.$ Number of stages at total reflux

b$.(\frac{L}{D}{)}_{\text{m}\text{i}\text{n}}$

c$.($L$/$D$)$ actual