Differential Costs and Sunk Costs Which one of the following statements is incorrect?

a. Sunk costs should be irrelevant in decision making.

b. Differential costs are the costs a company should consider when making decisions.

c. Differential costs cannot be reasonably avoided by a company.

d. Sunk costs are costs made in the past or committed in the future that do not pertain to future decisions.

e. Differential costs are sometimes called avoidable costs.