A mixture of methanol (Tb564C), ethanol (Tb578C), propanol (Tb597C), and butanol (Tb5117) with Met/Et52, Et/Prop51.9, and Prop/butanol53.5

A mixture of methanol (Tb564C), ethanol (Tb578C), propanol

(Tb597C), and butanol (Tb5117) with αMet/Et52, αEt/Prop51.9, and

αProp/butanol53.5 is to be separated into pure components. The molar rates (mol/s) are 6, 20, 5, and 4, respectively. Determine the optimal distillation sequence for ethanol as the main product.