Some management accounting experts argue that manufacturing costs are not inherently fixed or variable, but rather a function of the manner in which they are contracted. An example of a cost that is

traditionally classified as a fixed cost but behaves as a variable cost is:

A$.$ the wages of an assembly worker who is paid according to a piece rate system.

B$.$ the wages of factory workers who are paid based on the number of hours they work, but who do not go home when the factory is idle.

C$.$ the salary of a production supervisor who is paid the same salary regardless of the level of production.

D$.$ depreciation expense that is based on the number of units produced.