5.113 A merchant stocks a certain perishable item. She knows that on any given day she will have a demand for either two, three, or four of these items with probabilities 0.1, 0.4, and 0.5, respectively. She buys the items for $1.00 each and sells them for $1.20 each.

Any that are left at the end of the day represent a total loss. How many items should the merchant stock to maximize her expected daily profit?