Honeywell and Cootes law firm still uses pens and paper regularly rather than being a technology enabled company. They estimate that they use 30 pens a day with a daily standard deviation of 5 pens. These high quality pens costs roughly $5 per pen. It is estimated that the holding cost is 4% of the value of a pen a year. The assistant manager places orders for pens from Office Supplies Inc., with an estimated ordering cost to be $40. From the time the assistant manager places an order, it takes 5 days for the order to arrive. Assume 365 days per year, 52 weeks a year, and 7 days in a week.
What should the review period for these pens be (in years)?