An on-line drug store (ODS) sells 10,000 bottles of vitamins per month. It incurs a fixed order cost of $100 per order, and an annual holding cost of 20%. The manufacturer charges $3.00/bottle, and incurs $2.00/bottle in production, $250/order in shipping and handling, and 20% holding the inventory

If the manufacturer offers a 20% discount for a retailer order quantity above 6500, what is the optimal retailer order quantity? (choose the closest value)

7000

5000

6000

9000