A Motor Drives a Shaft with Diameter D = 46 $32 \mathrm { MPa }$

A motor drives a shaft with diameter d = 46 mm at f = 5.25 Hz and delivers P= 25 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) $91 \mathrm { MPa }$