Final answer:
The total relevant cost of reworking the defective units is the cost of rework ($8,000) plus the opportunity cost ($7,000), resulting in $15,000. This amount does not match any of the provided options.
Step-by-step explanation:
The total relevant cost of reworking the defective units for StarZinc Company at a unit cost of $40 can be calculated by multiplying the cost of reworking each unit by the number of defective units, which is 200. Thus, the total rework cost will be 200 units × $40 = $8,000.
However, since the defective units could be sold as is for $35 each, there is an opportunity cost of not selling them in their defective state. This opportunity cost is equal to the potential revenue from selling the defective units, which is 200 units × $35 = $7,000.
Therefore, the total relevant cost of reworking is the cost of rework plus the opportunity cost, which is $8,000 (rework cost) + $7,000 (opportunity cost) = $15,000.