Precision Paper Products produces both paper towels and paper napkins. The production process begins with the receipt and pulping of raw timber. Once the timber is pulped, it is screened, rolled, and dried into large rolls of paper. At this point, half the paper is cut and folded into napkins, while the other half is cut, perforated, and rolled into towels. Based on this description, which of the costs listed below would NOT be classified as a joint cost? A : The administrative costs associated with tracking and processing incoming timber shipments. B : The materials costs for the various chemicals involved in the pulping process. C : The direct labor costs associated with operation of the screening machine. D : The maintenance costs associated with the napkin folding machine.