A supply of geothermal hot water is to be used as the energy source in an ideal Rankine cycle, with R-134a as the cycle working fluid.  Saturated vapour R-134a leaves the boiler at a temperature of 85C, and the condenser temperature is 40C.  Assume a counterflowing heat exchanger arrangement. The geothermal water temperature should be equal to or greater than the R-134a temperature at any location inside the heat exchanger.  The point with the smallest temperature difference between the source and the working fluid is called the pinch point.  If 2 kg/s of geothermal water is available at 95C, what is the maximum power output of this cycle for R-134a as the working fluid? (Hint: split the heat exchanger C.V into two so that the pinch point with ΔT = 0, T = 85C appears.) 

The answer given is 15.2 kW.  I just have no idea how to get it. Please help!