Copr. Goedl Cincy Savers makes a single product. The sales price is $$90$ per unit; direct material is $$9$ per unit; direct labor is $$3$ per unit, overhead is $$6$ per unit and $$9,000$ per month; selling and administrative expenses are $$4$ per unit and $$22,000$ per month. The company produced $1,000$ units. Overhead is:

period

none of these

fixed

mixed