the value of the twisting moment (Tr ) will be

Question

If a solid circular shaft of steel 2 cm in diameter is subjected to permissible shear stress 10kN/cm². then the value of the twisting moment (T_r ) will be.  

(a) 10 KN-cm                 (b) 20 KN-cm

(c) 15 KN-cm                 (d) 5 KN-cm