The management of a large chain of frozen yogurt stores in New England believes that t days after the end of an adverti volume V of sales is approximated by 50,000-+ 50,000e - 0.43t At what rate (rounded to 2 decimal places) is the sales volume changing a. 3 days after the end of the advertising campaign? sales per day b. 4 days after the end of the advertising campaign? * sales per day