The quantity demanded each month of the walter serkin recording of beethoven's moonlight sonata, manufactured by phonola media, is related to the price per compact disc. the equation p = −0.00054x + 9 (0 ≤ x ≤ 12,000) where p denotes the unit price in dollars and x is the number of discs demanded, relates the demand to the price. the total monthly cost (in dollars) for pressing and packaging x copies of this classical recording is given by c(x) = 600 + 2x − 0.00002x2 (0 ≤ x ≤ 20,000)