The final amount is
[tex]\begin{gathered} A=P(1+\frac{R}{n\times100})^{nT} \\ Here,\text{ A is the final amount, P is the principal or the money earned by Kelsey, T is time in years, n is the number of tnes the comound interest is taken.} \end{gathered}[/tex]Here,A=400, R=5%, N=4,T=7. We have to find the principal.Substituting the values,
[tex]\begin{gathered} 400=P(1+\frac{5}{4\times100})^{4\times7} \\ \text{ 400=P(1+}\frac{5}{400})^{28} \\ \text{ P=}\frac{400}{\text{(1+}\frac{5}{400})^{28}} \\ \text{ =282.48} \end{gathered}[/tex]Therefore, the money earned by Kelsey doing odd jobs is 282.48.
