In determining the cost of a joban order for products or servicesit is not difficult to find the exact cost of materials and labor used directly (in measurable quantities) to make the products or perform the services. It is, by contrast, difficult or impossible to find the exact cost of overhead (rent, utilities, miscellaneous supplies, factory supervision, facility costs, etc) used to make the products or perform the services. How do management accountants calculate a good estimate for overhead costs of a job, how do they know if they were right or wrong in their estimate, how and when do they correct their errors?