Williams Commuter Air Service realizes a monthly revenue represented by the following function, where R(x) is measured in dollars and the price charged per passenger is x dollars.
R(x) = 4800x - 120x2
(a) Find the marginal revenue R'(x).
R'(x) = ??
(b) Compute the following values.
R'(19) = ??
R'(20) = ??
R'(21) = ??
(c) Based on the results of part (b), what price should the airline charge in order to maximize their revenue?