8) When a management training company prices its seminar on management techniques at $400 per person, 1,000 people will attend the seminar. The company estimates that for each $5 reduction'in price, an additional 20 people will attend the seminar. ' a) How much should the company charge for the seminar per person in order to maximize its revenue? b) What is the maximum revenue? '9) Sketch a graph of a function f that is continuous on (00, so) and satises the following conditions. ' a) f' > 0 on (00, O), (4, 6), and (6, co), b)f' 0 on (moo, 0), (0, 5) and (6, 00). e) f\"