Saalfrank Corporation is considering two alternatives that are code-named M and N. Costs associated with the alternatives are listed below: Alternative M Alternative N Supplies costs $ 77,000 $ 68,000 Assembly costs $ 49,000 $ 49,000 Power costs $ 29,000 $ 44,000 Inspection costs $ 42,000 $ 31,000 Required: a. Which costs are relevant and which are not relevant in the choice between these two alternatives? b. What is the differential cost between the two alternatives?