11. A store starts a week with at least 3 PCS. The demand per week is estimated at 0 with probability .15,1 with probability .2,2 with probability .35,3 with probability .25, and 4 with probability .05. Unfilled demand is backlogged. The store's policy is to place an order for delivery at the start of the following week whenever the inventory level drops below 3 PCs. The new replenishment always brings the stock back to 5 PCs.

(a) Express the situation as a Markov chain.