A solid circular shaft needs to be designed to transmit a torque of $50 \mathrm{~N} . \mathrm{m}$. If the allowable shear stress of the material is $140 \mathrm{MPa}$, assuming a factor of safety of 2 , the minimum allowable design diameter in $m m$ is

(A) 8

(B) 16

(C) 24

(D) 32

A solid circular shaft needs to be designed to transmit a torque of $50 \mathrm{~N} . \mathrm{m}$. If the allowable shear stress of the material is $140 \mathrm{MPa}$, assuming a factor of safety of 2 , the minimum allowable design diameter in $m m$ is

(A) 8

(B) 16

(C) 24

(D) 32

127