Relevant and sunk costs

Relevant and sunk costs McKinnon Company’s plant manager is considering buying a new grinding machine to replace an old grinding machine or overhauling the old one to ensure compliance with the plant’s high-quality standards. The following data are available: 



Required
(a) What costs should the decision maker consider as sunk costs?
(b) List all relevant costs and when they are incurred.
(c) What should the plant manager do?Why?