Markowis Corporation sells three different models of mosquito Solution Unit contribution margin: This is the excess of sales per unit over its variable cost per unit. Weighted-average unit contribution margin: This is the aggregate of the product of individual sales mix and its related unit contribution margin. Weighted-average unit contribution margin Items Sales per unit (a) Variable cost per unit (b) Unit contribution (a-b = x) Sales mix (y) Weighted-average unit contribution margin (x .