Which of the following statement (s) is (are) true? (You may select more than one answer.) o Product costs are expensed on the income statement in the period incurred. o Direct labor is a manufacturing cost and product cost. o Conversion costs include direct labor and indirect material. o Nonmanufacturing costs are treated as period expense. o Average cost per unit increases as the activity level increases. o Total fixed cost decreases as level of activity decreases. A common cost is one type of indirect costs. A particular cost may be direct or indirect depending on the cost object