A buyer for Needless Markup, a famous "high-end" department store, must decide on the quantity of a high-priced women's handbag to procure in Italy for the following Christmas season. The unit cost of the handbag to the store is $30 and the handbag will sell for $150. Handbags not sold by the end of the season are purchased by a discount firm for $20. A detailed analysis of historical data shows that the number of handbags sold is described by a normal distribution with mean 300 and standard deviation 40. What is the optimal number of bags to be purchased?