YOU MAY USE CALCULATORS
A bookstore can obtain a certain gift book from the publisher at a
cost of $3 per book. The bookstore has been offering the book at a
price of $15 per copy and, at this price, has been selling 200 copies
a month. The bookstore is planning to lower its price to stimulate
sales and estimates that for each $1 reduction in the price, 20 more
books will be sold each month. At what price should the bookstore
sell the book to generate the greatest possible profit?