[tex]\bf \begin{array}{|c|ll} \cline{1-1} \textit{a\% of b}\\ \cline{1-1} \\ \left( \cfrac{a}{100} \right)\cdot b \\\\ \cline{1-1} \end{array}~\hspace{5em}\stackrel{\textit{6.5\% of 25000}}{\left( \cfrac{6.5}{100} \right)25000}\implies \stackrel{\textit{extra charge}}{1625}[/tex]