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): $64,400 per year Variable costs (supplies): $1.30 per maintenance hour Estimated usage by: Assembly Department 4,900 Fabricating Department 6,900 Packaging Department 11,200 Total maintenance hours 23,000 Actual usage by: Assembly Department 3,900 Fabricating Department 7,000 Packaging Department 10,400 Total maintenance hours 21,300