Quantity Discount : 28.75% to 36.25% off 5+ @ 28.75% : 573.62 + 103.25 (18%) = 676.87 10+ @ 32.50% : 543.43 + 97.82 (18%) = 641.25 15+ @ 36.25% : 513.24 + 92.38 (18%) = 605.62