Calculating shear stress and angle of twist

A stepped shaft of uniform material has two diameters of 60mm and 50mm. The large diameter is built in and has a length of 600mm and the smaller diameter is 400mm. If the material modulus is 80GN/m2 and a torque of 38 Nm is applied at the smaller, what is the maximum shear stress in each part of the shaft and the angle of twist?

Explain and show calculations.