A manager at a car wash company in Missouri wants to measure the effectiveness of price discounts and various types of advertisement expenditures on sales. For the analysis, he uses varying price discounts (Discount) and advertisement expenditures on radio (Radio) and newspapers (Newspaper) in 40 counties in Missouri. A portion of the monthly data on sales (in $ 1,000s), price discounts (in percent), and advertisement expenditures (in $ 1,000s) on radio and newspapers are shown in Table 15.8; the complete data are available on the text website, labeled Car wash. At the 5% level, determine if the advertisement expenditures on radio and newspaper have a significant influence on sales.