Every decision involves choosing from among at least two alternatives. To be successful in decision making, managers must be able to tell the difference between relevant and irrelevant data and must be able to correctly use the relevant data in analyzing alternatives. REQUIRED: (a) To be relevant, a cost or revenue must not only be a future item but must also differ from one alternative to another. Explain the statement. (b) Explain why depreciation on an existing asset is always irrelevant. (c) Explain whether direct materials never be relevant in a make or buy decision