Consider a perfectly competitive industry initially in the long-run equilibrium. If all firms in the industry are required to adopt costly antipollution devices, the long-run effects would be that the firms would be earning and the industry will be producing amounts of output.

Aaron corporation, which has only one product, has provided the following data concerning its most recent month of operations: selling price $ 102 units in beginning inventory 0 units produced 4,900 units sold 4,260 units in ending inventory 640 variable costs per unit: direct materials $ 20 direct labor $ 41 variable manufacturing overhead $ 5 variable selling and administrative expense $ 4 fixed costs: fixed manufacturing overhead $ 64,200 fixed selling and administrative expense $ 2,900 the total contribution margin for the month under variable costing is: