Clostridium beijerinckii is a gram-positive, rod-shaped, motile bacterium. Its BA101 strain can ferment starch from corn to a mixture of acetone (A), n-butanol (B), and ethanol (E) at 37C under anaerobic conditions, with a yield of more than 99%. Typically, the molar ratio of bioproducts is 3(A):6(B):1(E). When a semidefined fermentation medium containing glucose or maltodextrin supplemented with sodium acetate is used, production at a titer of up to 33 g of bioproducts per liter of water in the broth is possible. After removal of solid biomass from the broth by centrifugation, the remaining liquid is distilled in a sequence of distillation columns to recover: 

(1) Acetone with a maximum of 10% water; 

(2) Ethanol with a maximum of 10% water; 

(3) N-butanol (99.5% purity with a maximum of 0.5% water); and 

(4) Water (W), which can be recycled to the fermentation reactor. If the four products distill according to their normal boiling points in C of 56.5 (A), 117 (B), 78.4 (E), and 100 (W), devise a suitable distillation sequence using the heuristics of §1.7.3.