At the end of an advertising campaign, weekly sales declined according to the equation y 13,000(5-0.05x) dollars, where x is the number of weeks after the end of the campaign. a. Determine the sales at the end of the ad campaign. b. Determine the sales 4 weeks after the end of the campaign. c. Does this model indicate that sales will eventually reach $0? a. The sales at the end of the campaign are $ (Round to the nearest cent as needed.)