Quantity Discount : 28.75% to 36.25% off 5+ @ 28.75% : 558.52 + 100.53 (18%) = 659.05 10+ @ 32.50% : 529.13 + 95.24 (18%) = 624.37 15+ @ 36.25% : 499.73 + 89.95 (18%) = 589.68