A company that produces cell phones has a cost function of $C(x)=(x-325{)}^2(x+452{)}^2-3\mathrm{.}7{10}^9,$

where $C(x)$ is cost in dollars and $x$ is number of cell phones produced $($in thousands$).$ How many units of cell phone $($in thousands$)$ minimizes this cost function?

with fully explanation please