The size of the bookstore is classi ed as Small, Medium and Large. A double sampling was performed to esti- mate the total sales of a certain book last month in the center county region, which has 500 bookstores. In the 100 book- stores selected randomly in the rst phase, 50 are small, 30 are medium and 20 are large. Suppose a strati ed random sample of 10 small, 6 medium and 4 large bookstores are carried out, the sales of the book title are