A stream of hot water at 85^◦C and a rate of 1 kg/s is needed for the pasteurizing unit in a milk-bottling plant. Such a stream is not readily available, and will be produced in a well-insulated mixing tank by directly injecting steam from the boiler plant at 10 bar and 200^◦C into city water available at 1 bar and 20^◦C. 

a. Calculate the flow rates of city water and steam needed. 

b. Calculate the rate of entropy production in the mixing tank.