The demand for next year's wildlife calendar at a bookstore is assumed to be normally distributed with a mean of 510 and a standard deviation of 80 . The calendar costs the bookstore $4.20 each and will be sold for $15 each. Any calendars remaining for sale after Christmas will be discounted and sold for $0.7 each. The bookstore believes any calendar remaining to be sold after Christmas can be cleared at the $1 price. How many wildlife calendars should the bookstore stock if it wants to maximize its expected profit from wildlife calendars?