In a flexible balloon, $2$ moles of $\mathrm{S}{\mathrm{O}}_2$ having an initial volume of $1 \mathrm{kL}$ at a temperature of $27 °\mathrm{C}$ is filled. The gas is first expanded to thrice its initial volume isobarically and then further expanded adiabatically so as to attain its initial temperature. Assuming the gas to be ideal, the work done by the gas in the whole process is [${\mathrm{\gamma }}_{{\mathrm{SO}}_2}=\raisebox{1ex}{$9$}\!\left/ \!\raisebox{-1ex}{$7$}\right.$, $\mathrm{R}=\frac{25}{3}\mathrm{ }\mathrm{J}\mathrm{ }{\mathrm{mol}}^{-1}\mathrm{ }{\mathrm{K}}^{-1}$]