The annual demand for a product has been projected at 2,000 units. this demand is assumed to be constant throughout the year. the ordering cost is $20 per order, and the holding cost is 20 percent of the purchase cost. the purchase cost is $40 per unit. there are 250 working days per year. currently, the company is ordering 500 units each time an order is placed. assuming the company uses a safety stock of 20 units resulting in a reorder point of 60 units, what is the expected lead-time for delivery