Managers routinely face the problem of deciding how constrained resource are going to be used. A department store, for example , has a limited amount of floor space and there fore cannot stock every product that may be available. A manufacturer has a limited number of machine- hour and a limited number of direct labor-hour at its disposal. When a limited resource of some type restricts the company’s ability to satisfy demand the company has a constraint. Because the company cannot fully satisfy demand, managers must decide which products or services should be cut back. In other words, managers must decide which products or services make the best use of the constrained resource. Fixed costs are usually unaffected by such choices, so the course of action that will maximize the company’s total contribution margin should ordinarily be selected.