Answer:
The correct option is b. irrelevant cost.
Step-by-step explanation:
An irrelevant cost can be described as an expense that will not be affected by the decisions of thee management. Therefore, irrelevant costs are those that will not change if you choose one option over another in the future.
Therefore, the $4,000 of annual operating costs that are common to both the old and the new machine are an example of irrelevant cost. This is because the 4,000 of annual operating costs will not be affected or will still be incurred whether Jarett Motors managment decide to keep its existing car washing machine or purchase a new one.
Therefore, the correct option is b. irrelevant cost.