Operations Management (10th edition) A store faces demand for one of it popular at a constant rate of 9,000 units per year. It costs the store $120 to process an order to replenish stock and $30 per unit per year to carry the item in inventory. A shipment from the supplier is typically received 14 working days after and order is placed. The store buys the product for $130 per unit and sells it for $210 per unit. A the moment the store uses an order quantity of 900 units. Assume model assumption are satisfied and 300 days a year