18. We need 20,000 units of a certain part to use in its production cycle. If we buy the part from a sourcer instead of making it, we cannot use the excess capacity for another manufacturing activity. Forty percent of the fixed overhead will continue regardless of what decision is made. Cost for us to make the part: (per unit) Direct materials S12 Direct labor S26 Fixed overhead $10 Cost to buy the part from another firm - $42 per unit A. In deciding whether to make or buy the part, our total relevant costs to make the part are a. $760,000 b. $840,000 C. $880,000 d. $960,000 B. . What decision should we make, and what is the total cost advantage that would result? a. Make / $40,000 b. Make / $120,000 C. Buy / $80,000 d. Buy / $40,000