Answer
$Q(t)=2000*e^{-0.1386t}$
Work Step by Step
The exponential decay model is the following:
$Q(t)=Q_0*e^{-t_s*k}$
Where $t_s*k=\ln2$, where $t_s$ is the half-life at $t=0$ and $k$ is constant.
$Q_0=2000$
$t_s*k=\ln2$
$5*k=\ln2$
$k=\frac{\ln2}{5}=0.1386$
Therefore the model follows the equation of:
$Q(t)=2000*e^{-0.1386t}$
