An insulated piston-cylinder device contains 0.05m3 of saturated refrigerant-134A vapor at 0.8mPa pressure. The refrigerant is now allowed to expand in a reversable manner until the pressure drops to 0.2mPa. Determine the change in the exergy of the refrigerant during this process and the reversable work. Assume the surroundings to be at 25 degrees C and 100kPa.