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

• A. \[{{10}^{5}}\,\]cal
• B. \[{{10}^{4}}\]cal
• C. \[{{10}^{3}}\] cal
• D. \[5\times {{10}^{3}}\]cal