Calculating and Using a Single Charging Rate The expected costs for the Maintenance Department of Stazler, Inc., for the coming year include: Fixed costs (salaries, tools): $75,820 per year Variable costs (supplies): $1.30 per maintenance hour Estimated usage by: Assembly Department 4,600 Fabricating Department 6,700 Packaging Department 11,000 Total maintenance hours 22,300 Actual usage by: Assembly Department 3,275 Fabricating Department 6,800 Packaging Department 10,200 Total maintenance hours 20,275