$5\mathrm{.}20$ A $3$$,25$ hp$,460$ V$,60$ Hz$,1760$ rpm$,$ wound$-$rotor induction motor has the following equivalent circuit parameters: R$1=0$:$25,$ X$1=1$:$2$ R$02=0$:$2,$ X$02=1$:$1$ Xm $=35$:$0$ The motor is connected to a $3$$,460$ V$,60$ Hz$,$ supply. $($a$)$ Determine the number of poles of the machine. $($b$)$ Determine the starting torque. $($c$)$ Determine the value of the external resistance required in each phase of the rotor circuit such that the maximum torque occurs at starting. Use Thevenin$$s equivalent circuit