hmmm now this is assuming is 3.1% per year, with a compounding period per week, now there are 52 weeks in a year.
[tex]~~~~~~ \textit{Compound Interest Earned Amount} \\\\ A=P\left(1+\frac{r}{n}\right)^{nt} \quad \begin{cases} A=\textit{accumulated amount}\\ P=\textit{original amount deposited}\dotfill &\$4200\\ r=rate\to 3.1\%\to \frac{3.1}{100}\dotfill &0.031\\ n= \begin{array}{llll} \textit{times it compounds per year}\\ \textit{weekly, thus fifty two} \end{array}\dotfill &52\\ t=years\dotfill &5 \end{cases}[/tex]
[tex]A=4200\left(1+\frac{0.031}{52}\right)^{52\cdot 5}\implies A=4200\left( \frac{52031}{52000} \right)^{260}\implies A\approx 52775.70[/tex]
