Sales and advertising the number of daily sales of a product was found to be given by
S = 100xe(-x)3 + 100
x days after the start of an advertising campaign for this product.
(a) Find the average daily sales during the first 20 days of the campaign-that is, from x = 0 to x = 20.
(b) If no new advertising campaign is begun, what is the average number of sales per day for the next 10 days (from x = 20 to x = 30)?