The following data relate to a company that produces and sells a travel guide that is updated monthly: Fixed costs: Copy editing Art work $ 6,000 2,000 Typesetting 72,000 Variable costs: Printing and binding $3.20 per copy Bookstore discounts 4.00 per copy Salespersons' commissions 0.50 per copy Author's royalties 2.00 per copy Each book sells for $20.00. The company sold 8,000 books in June and 10,000 books in July. The contribution margin ratio for the book is