Use

(a) variable costs,

(b) fixed costs,

(c) semivariable costs, and

(d) step-pattern costs to classify each of the following costs based on its cost behavior. Provide a brief explanation of your answer.

a. Direct materials b. Direct labor c. Depreciation d. Salary of production supervisor e. Telephone expense f. Machine repairs g. Factory janitor wages h. Property taxes i. Sales commissions j. Material handling