Williams Commuter Air Service realizes a monthly revenue represented by the following function, whereR(x) is measured in dollars and the price charged per passenger isxdollars.

R(x) =4400x-110x²

(a) Find the marginal revenueR'(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?

$