How do we found the specific internal energy (h) values from the steam tables according to this solution?

A heat exchanger, shown in the figure, is used to cool an air flow from 700 to 400 K, with both states at 1 MPa. The coolant is a water flow at 20C and 100 kPa. If the water leaves as saturated vapor at a mass flow rate of 0.5 kg/s, find the mass flow rate of air. For air, the specific heat ratio under constant pressure is 1004 J/kgK