Five bookstores open shop in a small city. Within a month, Bookstore A sells 1,000 books; Bookstore B sells 4,000; Bookstore C sells 6,000; and Bookstore E sells 7,000. Significantly, Bookstore A's hours are 12:00 p. m.-5:00 p. m.; Bookstore B's are 10:00 a. m.-5:00 p. m.; Bookstore C's are 9:00 a. m.-5:00 p. m.; and Bookstore E's are 9:00 a. m.-8:00 p. m. According to your line graph, all other factors remaining equal, how many books would Bookstore D have sold that month if its hours of business are 9:00 a. m.-6:00 p. m.? (Round your answer to the nearest 500.)