80 Suppose the demand function for x thousand of a certain item is p 100 where x 1 and p is in dollars In x a Find the marginal revenue b Find the revenue from the next thousand items at a demand of 9000 x 9 80 80 a The marginal revenue function is R x 100 Inx Inx Use integers or fractions for any numbers in the expression b The revenue from the next thousand items when x 9 is Type an integer or decimal rounded to two decimal places as needed