4. (20 points) A producer estimated the dependence of sales volume on advertising expenditures and priced as follow: Q = 35,000 - 5,000 P + 0.8 A - 0.000025 A2 where Q is the monthly quantity sold, P the price and A the monthly level of advertising. The average cost is constant at $2.65 (and hence equal to marginal cost) between 5,000 and 20,000 units produced per month and there is no xed cost other than the advertising expenditures. Right now, the price is xed by a 60% mark-up over average cost or P = 1.60 * 2.65 = $4.24 and the advertising expenditures amount to $9,000 per month. 4.1. At the actual level of advertising of $ 9,000 is the $ 4.24 price prot-maximizing? If not, determine the prot-maximizing price and the maximum amount of prot. 4.2. At the actual price of $ 4.24 what would be the prot-maximizing level of advertising expenditures and what would be the maximum amount of prot? 4.3. Verify if the Dorfman-Steiner condition is satised for a level of advertising of $ 8.524 and a price of$ 5.33