Ammonia vapor initially at 1 bar and 20°c fills a rigid vessel with a volume of 15 liters. the vapor is cooled until the temperature becomes -40°c. there is no work during the process. for the ammonia, determine the heat transfer and the change in exergy, each in kj. let to= 20°c, po= 1 bar and ignore the effects of motion and gravity. determine: (a) the heat transfer. (b) the change in exergy for the process.