A bookstore has a stock of 30 paperback copies of Surveying as well as 50 hardcover copies of the same book.

A bookstore has a stock of 30 paperback copies of Surveying as well as 50 hardcover copies of the same book. They wish to increase their stock for the new semester. Based on past experiences they want their final numbers of paperback and hardcover copies to be in the ratio of 4 to 3. However, the publisher stipulates that they will only sell the store 2 copies of the paperback edition for each copy of the hardcover edition ordered. Under these conditions, how many paperback should the store order to achieve the ratio of 4 to 3?