1. The problem asks to identify the meaning of avoidable costs and common mistakes in relevant costing. 2. Avoidable costs are costs that can be eliminated if a particular decision is made. They are also known as differential costs because they differ between alternatives. 3. Committed costs are costs that cannot be changed in the short term, uncontrollable costs are costs that management cannot influence, and sunk costs are past costs that cannot be recovered. 4. Therefore, avoidable costs are also called differential costs. 5. For the second question, relevant costing involves considering costs that will be affected by a decision. 6. A common mistake is including sunk costs, which are past costs and should not affect current decisions. 7. Future variable costs, future avoidable fixed costs, and opportunity costs are relevant and should be considered. Final answers: - Avoidable costs are also known as differential costs. - A common mistake in relevant costing is including sunk costs.