production manager uses the economic lot size approach to determine the batch size for a product with a weekly demand of 2000. the setup cost for each batch is $100 and once the setup is complete, the product may be produced at the rate of 500 units per day. there is a holding cost of $1 per unit per year and the plant operates 5 days a week on a 300-day production year. what is the optimal production lot size? what is the annual total cost of inventory? what is the time between two orders?