A drill press was purchased 4 years ago for $40,000. It's estimated salvage value after 7 years was $5,000. The press can be sold today for $15,000 or fir $12,000, $9,000, or $6,000 at the ends of each of the next 3 years. The annual operating and maintenance cost for the next 3 years will be $2,700 for this year and increase by $800 per year. What is the marginal cost for each year?