The catalog operation of a large clothing company sends out four regular catalogs per year and one summer sale catalog. Management has recently conducted a pricing test on their line of children's T-shirts. The test was carried out with their annual summer sale catalog. The T- shirts are usually discounted to $12.99 in this catalog. For this test, the first customer on the mailing list received a catalog with the T-shirts priced at $12.99, the second customer on the mailing list received a catalog with the T-shirts priced at $10.99. The third customer received the $12.99 catalog, the fourth received the $10.99 catalog, and so on throughout the entire 500,000 customer mailing list. The sales results of this test are as follows: