For The Make or Buy Decision, the example was Essex Company manufactures an input that is used in one of its products. The unit product cost of this part is given. While for variable and absorption costing, both types of costing systems do not include some of the per-unit costs listed in the relevant costing unit like --> Deprecation of special equipment, supervisor's salary and general factory overhead. So if the question about relevant costs doesn't say which type of costing it uses, which out the 3 ways to calculate unit product cost do we use when doing relevant decisions - for the unit product cost of $__ in relevant costing decisions, why do you include Deprecation of special equipment, supervisor's salary and general factory overhead while in absorption and variable costing, you include fewer items?