If a company makes two products, r1 and r2, what is the formula for the weighted-average unit contribution margin? (unit contribution margin of r1) + (unit contribution margin of r2). (unit contribution margin ratio of r1) + (unit contribution margin ratio of r2). (unit contribution margin of r1 x sales mix percentage of r1) + (unit contribution margin of r2 x sales mix percentage of r2). the correct formula is not listed above.