A 5-gallon tank used by a refrigerator repair person that initially contains a two-phase mixture of R134a at 20°C develops a small leak at the top. The process is slow enough such that the temperature remains constant at 20°C. If the initial contents are 90% liquid by mass, then determine the heat transfer (kJ) that occurred over the time it took for all the liquid to disappear in the tank (i. e. final state of saturated vapor at 20°C).