Suppose that for a certain city the cost C, in dollars, of obtaining drinking water that contains

Question:

Suppose that for a certain city the cost C, in dollars, of obtaining drinking water that contains p percent impurities (by volume) is given by
C = 120,000 / p - 1200
(a) Find the rate of change of cost with respect to p when impurities account for 10% (by volume).
(b) Write a sentence that explains the meaning of your answer in part (a).