help with this electronics problem?

10.- A three-phase motor connected in a star with two poles of 56 KW, 3560 rpm, 460 V and 60Hz, has the following parameters: Rs = 0, Rr = 0.08Ω, Xs = 0.13 Ω, Xr = 0.2 Ω and Xm = 11.4 Ω. The motor is controlled by varying the power frequency. If the breaking torque requirement is 160Nm, calculate: (a) the supply frequency and (b) the speed “wm” at maximum torque.