The following costs result from the production and sale of 4,600 drum sets manufactured by Tight Drums Company for the year ended December 31, 2017. The drum sets sell for $310 each. The company has a 25% income tax rate. Variable production costs Plastic for casing $133,400 432,400 174,800 Wages of assembly workers Drum stands Variable selling costs Sales commissions 124,200 Fixed manufacturing costs Taxes on factory Factory maintenance Factory machinery depreciation Fixed selling and administrative costs Lease of equipment for sales staff Accounting staff salaries Administrative management salaries 9,000 18,000 78,000 18,000 68,000 148,000 TIGHT DRUMS COMPANY Contribution Margin Income Statement (partial) For Year Ended December 31, 2017 Per Unit Sales Variable costs: Total variable costs Contribution margin