A company estimates that it will sell Nx units of a product after spending x thousand dollars on advertising,as given by
Nx=-4x+300x-3100x+18000, 10x40
(A)Use interval notation to indicate when the rate of change of sales N'x is increasing.
Note:When using interval notation in WeBWorK, remember that:You use'l'for co and-I'for-co,and 'U' for the union symbol. If you have extra boxes,fill each in with an 'x'.
N'(x)increasing
(B)Use interval notation to indicate when the rate of change of sales
N'(x)is decreasing. Nxdecreasing:
(C)Find the average of the x values of all inflection points of N(x).
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=