A rigid insulated tank of 1m3 containing oxygen at 500K and 1MPa is connected through a valve to a second insulated tank of 2m3 containing nitrogen at 800K and 2MPa. Valve between the two tanks is opened allowing the gases to mix and to reach the equilibrium state. Assuming oxygen and nitrogen to behave as an ideal gas with the gamma of 1.4 , estimate the change in entropy of oxygen and nitrogen