24. Which of the following is an example of direct materials cost for an automobile manufacturer? a. cost of oil lubricants for factory machinery b. cost of wages of assembly worker c. salary of production supervisor d. cost of interior upholstery 25. A plant manager's salary is a(n) a. direct cost and an indirect cost b. direct cost c. indirect cost d. period cost 26. If the cost of a direct material is a small portion of total production cost, it may be classified as part of a. direct labor cost