Tirri Corporation has provided the following information: Cost per Cost per unit period $7.55 $3.95 $1.60 Direct materials Direct labour Variable manufacturing overhead Fixed manufacturing overhead Sales commission $24,500 $1.10 $0.65 Variable selling and administrative expense Fixed selling and administrative expense $8,900 If the selling price is $28.20 per unit, the contribution margin per unit sold is closet to: $13.35 $10.05 $16.70 $8.15