Okay, here we have this:
Considering the provided information we are going to replace in the formula of continuous compound interest:
[tex]\begin{gathered} A=Pe^{rt} \\ 3500=Pe^{(0.065\cdot4)} \end{gathered}[/tex]Now, let's solve for P:
[tex]\begin{gathered} P=\frac{3500}{e^{0.26}} \\ P=$2,698.68$ \end{gathered}[/tex]Finally we obtain that should be invested $2,698.68.