Home Decorators Inc. is an online retailer that sells an exclusive Christmas gift item at a price of $400. They purchase the gift from an Asian supplier at a cost of $100. Demand for the item is normally distributed with a mean of 500 and standard deviation of 200. Any item left over at the end of the Christmas season is sold at a deep discount price that is 10% of the regular price. 

 What is the understocking cost per unit? What is the overstocking cost per unit? How many units of the gift item should Home Decorators Inc. order so as to maximize expected profits?