A Motor Drives a Shaft with Diameter $d=46 \mathrm{~mm} \text { at } f=5.25 \mathrm{~Hz}$

A motor drives a shaft with diameter $d=46 \mathrm{~mm} \text { at } f=5.25 \mathrm{~Hz}$ and delivers $P=25 \mathrm{~kW}$ of power. The maximum shear stress in the shaft is approximately: (A) $32 \mathrm{MPa}$
(B) $40 \mathrm{MPa}$
(C) $83 \mathrm{MPa}$
(D) $91 \mathrm{MPa}$