One mole of liquid A at 1000 K is added into a very large quantity of liquid A-B solution with X_A=0.25, isothermally. In this process, 9000 J of heat is supplied. If A-B solution is regular, calculate for X_A=0.5 at 900 K:

a) The values of H^M, H^M_A, S^M_A and y_A in above liquid A-B solution.

b) Discuss the behavior of components (positive or negative deviation) in liquid A-B solutions.