Refrigerant 134-a is contained in a 4 ft^3 tank at 160 lpf/in^2. At the beginning, the saturated vapour occupies a volume of 2 ft^3 and the remaining portion is filled with the saturated liquid. A valve is opened to allow escaping some saturated vapour. When the valve is closed the volume is 1ft^3 . The pressure is constant in this process. Determine: a) mass of the refrigerant that has escaped in lb b) the heat transferred during this process in BTU.