A composite shaft is made of a steel tube with an inner brass core perfectly bonded together as shown in the figure below. The shaft is fixed at one end and subjected to a torque of 2T at the other end. Shear modulus of steel is G and that of brass is G/2. The outer radius of the steel tube is R = 2r and radius of the inner brass core is r. The torque carried by the outer steel tube is (a) (c) 15T 31 2T 31 Steel Brass core (b) (d) a a 2T R = 2r 60 T 31 30 T 31 Section a - a