Routsong Company had the following sales and production data for the past four years: Production units Sales units Year 1 6,000 Year 2 Year 3 Year 4 9,000 4,000 5,000 6,000 6,000 5,000 7,000 Selling price per unit, variable cost per unit, and total fixed cost are the same in each year. Because of the changes in production levels, under absorption costing the unit product cost will change each year