P$4\mathrm{.}17$ By how much should the internal emf of the generator of the previous problem be changed so that it operates at unity power factor?

P$4\mathrm{.}18$ A generator synchronized to the grid operates at its nominal voltage. The field current is adjusted so that the magnitude of the internal emf is $1\mathrm{.}4$ pu $.$ Given that the synchronous reactance has a value of $0\mathrm{.}65$ pu and that the generator operates at unity power factor, calculate the active power produced by this generator, the power angle, and the magnitude and phase of the stator current. Use the terminal voltage as the reference for the angles.