Answer:
the revenue function = x · P(x) - C(x) = x · (211 − 5x) - (1,401 + 16x) = 211x - 5x² - 1,401 - 16x = -5x² + 211x - 16x - 1,401
R(x) = -5x² + 195x - 1,401
maximum revenue will be obtained for R'(x)
R'(x) = 2 · -5x + 195 = -10x + 195 = 0
195 = 10x
x = 19.5
the production level that yields a maximum profit should be 19.5
maximum monthly revenue
R(x) = -5·19.5² + 195·19.5 - 1,401 = -1,901.25 + 3,802.50 - 1,401 = $500.25