A rigid vessel of 0.06 m³ volume contains an ideal gas, C_V = (5/2)R, at 500 K and 1 bar.

a.) If heat in the amount of 15000J is transferred to the gas, determine its entropy change.

b.) If the vessel is fitted with a stirrer that is rotated by a shaft so that work in the amount of 15000 J is done on the gas, what is the entropy change of the gas if the process is adiabatic? What is ΔS_total? What is the irreversible feature of the process?