not sure how to calculate when given

Question 8 (8 points) Saved Deluxe Motors owns a Bobcat skid steer, today it is currently worth $21,000. Looking to the future they believe it will go down in value by 14% every year. Their operating and maintenance costs for the skid steer will be $1.953 this year and they will increase by $633 every year. Use an interest rate of 7% / yr. What is their marginal cost for year 3? NOTE: Marginal Costs are year-by-year estimates of the costs to own an asset for that particular year and you'll need to take into account all of the information given above. $6,648 $3,219 $5,393 $6,413 $6,481