Dan McClure owns a thriving bookstore. He must decide how many copies to order of a new book. The book$$s retail price is $$20,$ its wholesale price is $$12,$ and the publisher will buy back unsold copies at a full refund but McClure will incur $$4$ in shipping and handling costs for each book. Dan believes demand for tDhe book is normally distributed with mean $200$ and std$.$ dev. $80.$a$.$Dan will consider this book to be blckbuster for him if it sells more than $400$ units