The following costs result from the production and sale of 1,000 drum sets manufactured by Tight Drums Company for the year ended December 31, 2015. The drum sets sell for $500 each. The company has a 25% income tax rate.

Variable production costs
Plastic for casing	$	17,000
Wages of assembly workers		82,000
Drum stands		26,000
Variable selling costs
Sales commissions		15,000
Fixed manufacturing costs
Taxes on factory		5,000
Factory maintenance		10,000
Factory machinery depreciation		40,000
Fixed selling and administrative costs
Lease of equipment for sales staff		10,000
Accounting staff salaries		35,000
Administrative management salaries		125,000
Compute its contribution margin per unit and its contribution margin ratio. Prepare a contribution margin income statement. Interpret the contribution margin and contrubition margin ratio.