What is the entropy increase per kilogram of the downstream river water?

Suppose a power plant delivers energy at 867MW using steam turbines. The steam goes into the turbines superheated at 638K and deposits its unused heat in river water at 287K. Assume that the turbine operates as an ideal Carnot engine. If the river flow rate is 39.1m3/s, calculate the average temperature increase (in Celsius) of the river water downstream from the power plant. Enter answer without units. I found the average temperature increase to be 4.33. and now it is asking what the entropy increase per kilogram is of the downstream river water and I can not seem to find the answer. Any suggestions?