Northern Star sells several products. Information of average revenue and costs is as follows: Selling price per unit $ 22.00 Variable costs per unit: Direct material $ 6.00 Direct manufacturing labor $ 1.80 Manufacturing overhead $ 0.50 Selling costs $ 3.00 Annual fixed costs $ 100 comma 000 The company sells 12 000 units at the end of the year. If direct labor and direct material costs increase by $ 1.00 each, contribution margin ________.

A. decreases by $ 24 000 .

B. increases by $ 24 000 .

C. increases by $ 12 000 .

D. decreases by $ 12 000