1. The problem asks about the nature of unavoidable fixed costs in a make-or-buy decision. 2. In cost accounting and decision-making, fixed costs are costs that do not change with the level of production or purchase. 3. Unavoidable fixed costs are those that will be incurred regardless of the decision made (whether to make or buy). 4. Because these costs cannot be avoided, they are considered irrelevant to the decision-making process. 5. Relevant costs are those that will change depending on the decision, such as future variable costs or direct materials. 6. Therefore, unavoidable fixed costs are irrelevant in a make-or-buy decision because they do not affect the incremental cost comparison. Final answer: Unavoidable fixed costs are Irrelevant.