$Ch.2$: Fixed $vs.$ Variable Cost Behavior $(E2-5B)$: Russell Company$s$ production and total cost data for two recent months follow. January February Units produced $1,000500$ Total depreciation cost $$6,000$ $$6,000$ Total factory supplies cost $$2,000$ $$1,000a.$ Separately calculate the depreciation cost per unit and the factory supplies cost per unit for both January and February. $b.$ Identify which cost $is$ variable and which $is$ fixed. $c.$ Assume that the units produced $in$ January were $800$ instead $of1,000.$ What would the total cost $of$ depreciation and factory supplies $bein$ this scenario?