A stepped shaft ABC, is 0.8 m long. For a length AB = 0.4 m, shaft diameter is 40 mm and for length BC = 0.4 m, shaft diameter is 20 mm. Shaft is fixed at both the ends A and C. At the Section B, a torque T is applied which causes a maximum shear stress of 100 MPa in stepped shaft. Determine the magnitude of torque T.