3. Which of the following is true of an opportunity cost? a. It is the difference between the summed costs of two alternatives in a decision. b. It is the cost that is not affected by any future action. c. It is the benefit sacrificed or foregone when one alternative is chosen over another. d. It is the cost that has already been incurred and cannot be recovered 1. Which of the followng is a cost that cannot be affected by any future action a. Opportunity cost b. Variable cost c. Relevant cost d. Sunk cost