Answer:
Overhead costs are assigned to production using an overhead application rate, whereas no such "application rate" is used to assign the costs of direct materials and direct labor to production. The reason for this difference in procedures is that:
Overhead is an indirect cost which cannot be traced easily and directly to specific units of product.
Step-by-step explanation:
Manufacturing overhead costs are not direct costs. They are not generally traceable to units of products. They include such indirect costs as Depreciation Expense, Property Taxes, Indirect Labor, Indirect Materials, etc. No unit of product can be ascribed such costs except as an approximation.