Feed-water heaters are used to increase the efficiency of steam power plants. A 20 kg/s stream of boiler feed water is heated from 25°C to 195°C at a pressure of 1400 kPa by mixing it with 30 kg/s of saturated steam at 195°C and 1400 kPa. The heater loses heat at a rate of 50 J/g of exiting mixture. What fraction of the exit stream is steam?