Given:
The initial amount is $8800.
The Future value is $15600.
Number of year = 5 years compounded quarterly .
The interest rate is calculated as,
[tex]\begin{gathered} FV=P(1+\frac{r}{4})^{4\times n} \\ 15600=8800(1+\frac{r}{4})^{4\times5} \\ \frac{39}{22}=(1+\frac{r}{4})^{20} \\ \sqrt[20]{\frac{39}{22}}=1+\frac{r}{4} \\ \frac{r}{4}=\sqrt[20]{\frac{39}{22}}^{}-1 \\ r=4(\sqrt[20]{\frac{39}{22}}-1) \\ r=0.1162 \end{gathered}[/tex]Answer: the interest rate is 0.1162.