Hoover Corporation produces and sells two models of vacuum cleaners, Standard and Deluxe. The company records show the following monthly data relating to these two products: Standard Deluxe Unit selling price 15,000 16,500 Unit Variable production costs 12,000 12,600 Unit Variable selling expense 1,600 1,300 Expected monthly unit sales 600 1,200 The company's total monthly fixed cost is 1,500,000. The firms overall contribution margin ratio is ________%.