The number of daily sales of a product was found to be given by S =100xe-x2 +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)?