well, keeping in mind a year has 12 months, thus 4 months is really 4/12 of a year
[tex]~~~~~~ \textit{Simple Interest Earned} \\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\\ P=\textit{original amount deposited}\dotfill & \$4200\\ r=rate\to 4.5\%\to \frac{4.5}{100}\dotfill &0.045\\ t=years\to \frac{4}{12}\dotfill &\frac{1}{3} \end{cases} \\\\\\ I = (4200)(0.045)(\frac{1}{3}) \implies I=63[/tex]
