Nation$-$Wide Bus Lines is proud of its six$-$week bus driver$-$training program that it conducts for all new Nation$-$Wide drivers. As long as the class size remains less than or equal to $35,$ a six$-$week training program costs Nation$-$Wide $$28,000$ for instructors, equipment, and so on$.$ The Nation$-$Wide training program must provide the company with approximately five new drivers per month. After completing the training program, new drivers are paid $$1,100$ per month but do not work until a full$-$time driver position is open. Nation$-$Wide views the $$1,100$ per month paid to each idle new driver as a holding cost necessary to maintain a supply of newly trained drivers available for immediate service.