A mixture of ideal gases has the following composition by mass:
$\begin{array}{|c|c|c|} \hline N_2 & O_2 & CO_2 \\ \hline 60\% & 30\% & 10 \% \\ \hline \end{array}$
If the universal gas constant is $8314 \: J/kmol-K$, the characteristic gas constant of the mixture (in $J/kg-K$) is ________