The specific heat of hydrogen gas at constant pressure is ${\mathrm{C}}_{\mathrm{P}}=3.4\times {10}^3\mathrm{cal}/\mathrm{kg}{}^{\mathrm{o}}\mathrm{C}$ and at constant volume is ${\mathrm{C}}_{\mathrm{V}}=2.4\times {10}^3\mathrm{cal}/\mathrm{kg}{}^{\mathrm{o}}\mathrm{C}.$ If one kilogram hydrogen gas is heated from  ${10}^{\mathrm{o}}\mathrm{C}$ to ${20}^{\mathrm{o}}\mathrm{C}$  at constant pressure, the external work done on the gas to maintain it at constant pressure is