In an experimental set-up, air flows between two stations P and Q adiabatically. The direction of flow depends on the pressure and temperature conditions maintained at P and Q. The conditions at station P are 150 kPa and 350 K. The temperature at station Q is 300 K. The following are the properties and relations pertaining to air: Specific heat at constant pressure, C_p = 1.005 kJ/kgK; Specific heat at constant volume, C_v = 0.718 kJ/kgK; Characteristic gas constant, R = 0.287 kJ/kgK Enthalpy, h = c_p T Internal energy, u = C_v T

If the pressure at station Q is 50 kPa, the change in entropy (s_Q - s_P ) in kJ/kgK is