15. Which one of the following statements regarding relevant costs is NOT true? a) Generally, a product line should be dropped when the fixed costs that can be avoided by dropping the product line are more than the contribution margin that will be lost another decision management has decided cannot be marketed represents a b) A cost that is relevant to one decision may not be relevant to c) The financial investment made in a research project that relevant cost for decision making. d) Avoidable costs are also called differential costs