A company estimates that it will sell N(X) units of a product after spending Sx thousand on advertising, as given by N(x) = -0.25x4 +22x-432x + 82,000, where 18 x48. When is the rate of change of sales increasing and when is it decreasing? What is the point of diminishing returns and the maximum rate of change of sales? Graph N and N' on the same coordinate system. The rate of change of sales is increasing on (Type your answer in interval notation.) The rate of change of sales is decreasing on (Type your answer in interval notation.) The point of diminishing returns is thousand dollars. sales per thousand dollars. The maximum rate of change of sales is (Round to the nearest whole number as needed.) Graph N and N' on the same coordinate system. Choose the correct answer below. A. B. 210000- N 0+ 13 N' 53 C. Q 210000- N 210000- N 13 N' 53 0+ 13 N' 53 D. Q 210000 N 13 N' 53