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 =

110,000

p

? 1100.

(a) Find the rate of change of cost with respect to p when impurities account for 1% (by volume). (b) Write a sentence that explains the meaning of your answer in part (a).

If impurities increase 1%, the cost will decrease $110,000.If impurities increase 11%, the cost will decrease $10,000. If impurities decrease 1%, the cost will decrease $110,000.If impurities increase 11%, the cost will increase $10,000.If impurities increase 1%, the cost will increase $110,000.