A closed container contains a homogeneous mixture of two moles of an ideal monatomic gas ($\mathrm{\gamma }$=5 / 3) and one mole of an ideal diatomic gas ($\mathrm{\gamma }$=7/5). Here, $\mathrm{\gamma }$ is the ratio of the specific heats at constant pressure and constant volume of an ideal gas. The gas mixture does a work of 66 Joule when heated at constant pressure. The change in its internal energy is $(120+\mathrm{n})$ Joule, then $\mathrm{n}$ is