The Junior League of Yadkinville, California, collected recipes from members and published a cookbook entitled Food for Everyone. The book will sell for $17 per copy. The chairwoman of the cookbook development committee estimated that the club needed to sell 8,600 books to break even on its $51,600 investment. What is the variable costs per unit assumed in the Junior Leagues analysis? (Round your answer to the nearest whole number.)

$ _ per unit