Tirri Corporation has provided the following information: Cost per Unit Cost per Period Direct materials $ 7.50 Direct labor $ 3.85 Variable manufacturing overhead $ 1.55 Fixed manufacturing overhead $ 24,400 Sales commissions $ 1.05 Variable administrative expense $ 0.60 Fixed selling and administrative expense $ 8,800 If the selling price is $28.10 per unit, the contribution margin per unit sold is closest to: