Question 4 (20 marks) Barbie's trading company sells Barbie's doll and the annual demand is 2800 doll. It costs the company $33 to place an order and the carrying cost is 7% of the unit cost. The cost of each doll is $40. The supplier offers the following discounts to Barbie's Company. Order Quantity Discount Unit Cost 200 8% $37.20 a) What would be the optimal order quantity? (18 marks) b) What is the minimum annual inventory cost? (2 marks)