#### Answer

$\{t\in \mathbb{R}\ |\ 0\leq t\leq 5\}$ or $[0,5]$

#### Work Step by Step

If a function is used as a model for an application, the problem situation may require restrictions on the domain. For example, length and time are generally nonnegative, and a person's age does not increase indefinitely.
$ V(t)=250-50t\quad$ can be calculated for any real number t,
but the sense of the problem is that we take only a nonnegative amount of time into account.
So, $t\geq 0.$
Also, the value $V(t)$ should not be negative, so we restrict t in terms of
$250-50t\geq 0$
$250\geq 50t$
$5\geq t$
Domain = $\{t\in \mathbb{R}\ |\ 0\leq t\leq 5\}$ or $[0,5]$