When deciding whether to accept a special order, we should compare the extra revenues we will receive against the extra costs we will incur to fill the order extra fixed costs we will incur to fill the order total costs of making the sunglasses . Costs that we will incur whether or not we fill the order are irrelevant relevant to our decision. This is why comparing the $ 67 price Vision Lenses offered us with our $ 75 total cost of making and selling the sunglasses is correct misleading . Part 4 Specifically, we have enough capacity to produce the 20,000 extra pairs of sunglasses for Vision Lenses' special order without increasing our fixed costs total costs variable costs . Our fixed costs total costs variable costs will continue to rise continue to lower remain the same whether or not we accept the order, so these costs are irrelevant relevant . Also, as you know, we will not incur any fixed costs variable MOH variable marketing expenses on the special order. These costs will be the same whether or not we make the additional 20,000 pairs of sunglasses for Vision Lenses