6. A counterflow heat exchanger operates at steady state with negligible kinetic and potential energy effects. In one stream, liquid water enters at 10 C and exits at 20 C with a negligible change in pressure. In the other stream, Refrigerant 134a enters at 10 bar, 80 C with a mass flow rate of 135 kg/h and exits at 10 bar, 20 C. The liquid water can be modeled as incompressible with c = 4.179 kJ/kg K. Heat transfer from the outer surface of the heat exchanger can be ignored. Determine (a) the mass flow rate of the liquid water, in kg/h. (b) the rate of entropy production within the heat exchanger, in kW/K.