As mentioned, direct costs are not always variable costs. Consider a company that makes home appliances and define an individual refrigerator as a cost object. Which of the following costs is a direct, fixed cost?

The salaries of full$-$time workers who assemble the refrigerators paid on a monthly basis, assuming no overtime allowance has been incurred

The salary of the maintenance staff in the workshop paid on the monthly basis

Sales commissions paid on a per unit$-$sold basis

The electricity costs that incur in the plant