In order to calculate the principal, we can use the formula for interest compounded continuously:
[tex]A=P\cdot e^{rt}[/tex]Where A is the final amount after t years, P is the principal, r is the interest rate and e is a constant equal to 2.7183.
So we have:
[tex]\begin{gathered} 3500=P\cdot2.7183^{0.038\cdot1.5} \\ 3500=P\cdot1.058656 \\ P=\frac{3500}{1.058656}=3306.08 \end{gathered}[/tex]So the principal is $3306.08.