Solve the Problem $$P(x)=-0.1 x^{5}+3.2 x^{4}+4000$$ Where $x$ Is Time in Years Since 1960

Multiple Choice

Solve the problem.
-Suppose that the population of a certain city during a certain time period can be approximated by:
$$P(x) =-0.1 x^{5}+3.2 x^{4}+4000$$
Where $x$ is time in years since 1960. By sketching a graph of $\mathrm{P}(\mathrm{x})$ , estimate during what time period the population of the city was increasing.

A) Between 1986 and 1992
B) Between 1965 and 1986
C) Between 1960 and 1973
D) Between 1960 and 1986