If it is a simple interest rate, it does not compound.
We can relate the present value PV and the future value FV as:
[tex]\begin{gathered} FV=PV(1+n\cdot r)=PV+I \\ I=PV\cdot n\cdot r \\ r=\frac{I}{PV\cdot n} \end{gathered}[/tex]r: annual interest rate.
I: interest ($ 300.56)
PV: present value or initial capital ($850)
n: number of periods (13.6 years)
Then, we can calculate r as:
[tex]r=\frac{I}{PV\cdot n}=\frac{300.56}{850\cdot13.6}=\frac{300.56}{11560}=0.026[/tex]The interest rate is r=0.026 or 2.6%.
