A mixing chamber operated at 300 kPa pressure and is designed to mix a stream of steam with a stream of water. Steam at a temperature of 160 C enters the mixing chamber, where it is mixed with water that flows in at a temperature of 20 C and a mass flow rate of 5 kg/s. At the exit of the mixing chamber the mixture has a temperature of 70 C. The mixing chamber is not fully insulated, so that it loses heat to the surroundings at a rate of 40 kW. The heat transfer takes place through a boundary temperature of 25 C. Calculate: a) the mass flow rate of steam, and b) the rate of entropy production.