Average Demand of Carpet(yards per month)

A warehouse distributor of carpet keeps 6,000 yards of deluxe shag carpet in stock during a month. The average demand for carpet from the stores that purchase from the distributor is 4,500 yards per month, with a standard deviation of 900 yards. What is the probability that a customer’s order will not be met during a month? (This situation is referred to as a stockout.)