A mixture of maleic anhydride and benzoic acid containing 10 mol% acid is a product of the manufacture of phthalic anhydride. The mixture is to be distilled continuously in a column with a total condenser and a partial reboiler at a pressure of 13.2 kPa (100 ton) with a reflux ratio of 1.2 times the minimum value to give a product of 99.5 mol% maleic anhydride and a bottoms of 0.5 mol% anhydride. Is this problem completely specified?