Suppose the demand function for x thousand of a certain item is p = 140 + In y , where x > 1 and p is in dollars. (a) Find the marginal revenue. (b) Find the revenue from the next thousand items at a demand of 7000 (x = 7) (a) The marginal revenue function is R'(x) = (Use integers or fractions for any numbers in the expression.) (b) The revenue from the next thousand items when x = 7 is $ (Type an integer or decimal rounded to two decimal places as needed.)