hello
to solve this question, we would use the formula of simple interest
[tex]\begin{gathered} si=\text{p(1+rt)} \\ p=\text{principal}=400 \\ r=\text{rate}=8\text{ \% = }\frac{8}{100}=0.08 \\ t=x \end{gathered}[/tex][tex]\begin{gathered} f(x)=400(1+0.08)^x \\ f(x)=400(1.08)^x \end{gathered}[/tex]
the answer to this question is option D
