Explanation
We are given the following:
[tex]\begin{gathered} initial\text{ }population(a)=8000 \\ r=4\%=0.04 \end{gathered}[/tex]We are required to determine the model with the given data.
We know that the model is an exponential function given as:
[tex]\begin{gathered} y=ab^x \\ where \\ b=1+r \end{gathered}[/tex]Therefore, we have:
[tex]\begin{gathered} y=ab^x \\ y=8000(1+0.04)^x \\ y=8000(1.04)^x \end{gathered}[/tex]Hence, the answer is:
[tex]y=8,000(1.04)^{x}[/tex]