Solve the Problem $$P(x)=x^{3}-18 x^{2}+81 x$$ Where $x$ Is Time in Years from the Date of the First

Multiple Choice

Solve the problem.
-Suppose that the change in pressure of the oil in a reservoir can be approximated by:
$$P(x) =x^{3}-18 x^{2}+81 x$$
Where $x$ is time in years from the date of the first reading. This function is valid for $0 \leq x<9$ . By sketching a graph of $\mathrm{P}(\mathrm{x})$ , estimate during what time period the change in pressure is decreasing.

A) In years 5 to 9
B) In years 3 to 9
C) In years 0 to 9
D) In years 0 to 3