[tex]\qquad \textit{Amount for Exponential Decay} \\\\ A=P(1 - r)^t\qquad \begin{cases} A=\textit{current amount}\\ P=\textit{initial amount}\dotfill &3500\\ r=rate\to 10\%\to \frac{10}{100}\dotfill &0.1\\ t=\textit{elapsed time}\dotfill &5\\ \end{cases} \\\\\\ A=3500(1-0.1)^5\implies A=3500(0.9)^5\implies A\approx 2066.72[/tex]