15·22A. (Fixed costs) Detroit Heat Treating projects that next year its fixed costs will total

$120,000. Its only product sells for $12 per unit, ofwhich $7 is a variable cost. The management of Detroit is considering the purchase of a new machine that will lower the variable cost per unit to $S. The new machine, however, will add to fixed costs through an increase in depreciation expense. How large can the addition to fixed costs be to keep the firm's break-even point in units produced and sold unchanged?