in a $2000$ V$.$ single$-$phase synchronous generator, a full$-$load current of $100$ A produced on short$-$circuit by a field excitation of $2\mathrm{.}5$ A$,$ an emf of $500$ V is produced on open$-$circuit by the same excitation. The armature resistance is $0\mathrm{.}8$ W Determine the voltage regulation when the generator is deliveing a current of $100$ A at $($a$)$ unity power factor, $($b$)071$ power factor lagging, and $($c$)08$ power factor leading