A company estimates that it will sell [math] units of a product after spending [math] thousand dollars on advertising, as given by [math]
(A) Use interval notation to indicate when the rate of change of sales [math] is increasing.

Note: When using interval notation in WeBWorK, remember that: You use 'I' for [math] and '-I' for [math], and 'U' for the union symbol.
If you have extra boxes, fill each in with an 'x'.

[math] increasing:


(B) Use interval notation to indicate when the rate of change of sales [math] is decreasing.

[math] decreasing:

(C) Find the average of the [math] values of all inflection points of [math].
Note: If there are no inflection points, enter -1000.

Average of inflection points =

(D) Find the maximum rate of change of sales.

Maximum rate of change of sales =