Fixed costs are to a business decision as a sunk cost is to a:

Fixed costs are expenses that a business must pay regardless of its level of production or sales, such as rent or salaries. When making decisions, businesses often ignore fixed costs because these costs will remain the same no matter what choice they make. In contrast, a sunk cost is money that has already been spent and cannot be recovered, such as an investment in equipment that is no longer useful. Just like fixed costs, sunk costs should not influence future business decisions since they cannot be changed. For example, if a company spends money on a marketing campaign that didn't work, that money is a sunk cost, and the company should focus on future strategies instead of dwelling on that loss.