Hello, can someone help me with this question, please?

The number of daily sales of a product was found to be given by S = 900xe^-x^2 + 900 x days after the start of an advertising campaign for this product. (Round your answers to one decimal place.) (a) Find the average daily sales during the first 80 days of the campaign-that is, from x = 0 to x = 80. (b) If no new advertising campaign is begun, what is the average number of sales per day for the next 10 days (from x = 80 to x = 90)