A 5.0-liter gas tank holds 1.4 moles of helium (monatomic) and 0.7 moles of oxygen (diatomic), at a temperature of 260 K. The atomic masses of helium and oxygen are 4.0 g/mol and 16.0 g/mol, respectively. The total random translational kinetic energy of the gas in the tank, in kJ, is closest to: