kubin company’s relevant range of production is 20,000 to 23,000 units. when it produces and sells 21,500 units, its average costs per unit are as follows: average cost per unit direct materials $ 8.00 direct labor $ 5.00 variable manufacturing overhead $ 2.50 fixed manufacturing overhead $ 6.00 fixed selling expense $ 4.50 fixed administrative expense $ 3.50 sales commissions $ 2.00 variable administrative expense $ 1.50