(b) Jack's Stationery store also carries a Colour Cartridge for Laser Printers that sells at an approximate constant rate of 500 units every three months. His current buying policy is to order 500 units each time he orders from a supplier. It costs Jack $120 to place an order. The annual holding cost rate is 20%. With the order quantity of 500 , Jack obtains the Colour Cartridges at the lowest possible unit cost of $112. Other quantity discounts offered by the supplier are as follows: (i) What is the minimum cost order quantity for the Colour Cartridges? (ii) What are the annual savings of your inventory policy over the policy currently being used by Jack