eoq with discounts - kaplan test your understanstanding 7

Dear Tutor, I need a help from you Question is as follows: Watton ltd is a retailer of beer barrels. The company has an annual demand of 36,750 barrels. the barrels cost $12 each. Fresh supplies can be obtained immediately, but ordering costs and the cost of carriage inwards are $200 per order. The annual cost of holding 1 barrel in inventory is estimated to be $1.20. The Economic Order Quantity has been calculated to be 3500 barrels. The suppliers introduce a quantity discount of 2% on orders of at least 5000 barrels and 2.5% on orders of at least 7500 barrels. It is required to determine whether the least cost order quantity is still the EOQ of 3500 barrels. As per Kaplan answer, Total costs of 3500 barrels are $445,200 Total costs of 5000 barrels are $436,650 Total costs of 7500 barrels are $435,455 But, if I can't understand why the discounts have not been calculated in the holding costs in Kaplan solution. As per my calculations, after watching your videos, I get $445,200, $436590 and $435342.50 respectively. Can you please help me understanding where I got it wrong. Kind Regards, Ashish