Tiffany owns a bookstore and wants to determine the fixed and variable costs associated with selling do-it-yourself books. She made a graph with the number of books sold on the x-axis and the costs associated with selling the books on the y-axis. Tiffany fitted a line to her plot and made special note of the where the line crossed the y-axis. What will this tell her? O The rate at which variable costs increase. O The value of her fixed costs. O The value of her variable costs. O How quickly books are sold