Ergonomics Inc. sells ergonomically designed office chairs. The company has the following information: 
 Average demand = 20 units per day 
 Average lead time = 30 days 
 Item unit cost = $50 for orders of less than 200 units 
 Item unit cost = $48 for orders of 200 units or more 
 Ordering cost = $25 
 Inventory carrying cost = 25% 
 The business year is 250days
 Required : 
 How many chairs should the firm order each time?