Western University Uses $136,000 of a Particular Toner Cartridge for Laser

Essay

Western University uses $136,000 of a particular toner cartridge for laser printers in the student computer labs each year. The purchasing director of the university estimates the ordering cost at $51 and thinks that the university can hold this type of inventory at an annual storage cost of 20% of the purchase price of $4 each. How many months' supply should the purchasing director order at one time to minimize the total annual cost of purchasing and carrying?