4. A company wants to decide whether to make its materials in-house or to sub-contract production to an external supplier. In the past it has made four materials in-house, but demand in the next year will exceed in-house production capacity of 8,000 units. All four materials are made on the same machines and require the same machine time per unit: machine time is the limiting production factor. The following information is available. Directly attributable fixed costs are fixed cash expenditures that would be saved if production of the material in-house is stopped entirely. If a decision is made solely on the basis of short-term cost considerations, what materials should the