Suppose that, due to hydrogen bonding, the system A + B forms a 1-1 complex in the vapor phase when mixed. Neither pure species self-associates in the vapor phase. The equilibrium constant for the solvation is K_AB = 0.8 bar^-1 at 80°C. At 80°C, a mixture with a apparent (bulk) mole fraction of y_A = 0.5 is all vapor at 0.78 bar. Calculate the fugacity coefficient of A in the vapor phase using ideal chemical theory at this composition, temperature, and pressure. Use hand calculations.