Chapter 13.3, Problem 39E

Sales and advertising The number of daily sales of a product was found to be given by

$S=100x{e}^{-x^2}+100$

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 $x=0\text{ to }x=20$.

(b) If no new advertising campaign is begun, what is the average number of sales per day for the next 10 days (from $x=20\text{ to }x=30$

)?