Absorption #$1$: Acetone$-$Oil Absorption

By means of a plate column, acetone is absorbed from its mixture with air in a non$-$volatile absorption oil. The entering gas contains $20\mathrm{.}0$ mole percent acetone, and the entering oil is acetone$-$free. Of the acetone in the air, $98\mathrm{.}5$ percent is to be absorbed$,$ and the concentration of the liquor at the bottom of the tower is to contain $5$ mole percent acetone. The equilibrium relationship is $y_e=1\mathrm{.}80x_e.$

Plot the operating line and determine the minimum number of stages.

Hint: Choose $100$ moles of entering gas as a basis.