(1 point) The total revenue (in dollars) from the sale x coffee machines is R(x) = 2400 + 40x 0.23:2. (A) Find the exact revenue from the sale of the 21 st machine. Exact revenue from the sale of the 21st machine = (B) Use marginal revenue to approximate the revenue the sale of the 21 st machine. Approx. revenue from the sale of the 21st machine = (Round answers to three decimal places as needed.)