A circular shaft subjected to torsion undergoes a twist of 10in a length of 120 cm. If the maximum shear stress induced is limited to 1000 kg/cm2and if modulus of rigidity G = 0.8 x 106then the radius of the shaft should be
(a) p/8
(b) p/27
(c) 18/p
(d) 27/p
(a) p/8
(b) p/27
(c) 18/p
(d) 27/p