Bella's Burgers sells burgers, fries, and milkshakes. Last month, Bella's Burgers sold $20,000 of burgers, which had associated variable costs of $8,000; $10,000 of fries, which had associated variable costs of $4,000; and $5,000 worth of milkshakes, which had associated variable costs of $2,000. Bella's Burgers had total fixed costs of $6,000. What is Bella's company-wide break-even point? a.) $10,000 b.) $21,000 c.) $35,000 d.) $15,000