A post-hole digger is mouted on a tractor. The power unit of the machine applies a torque of 800 lb.in to the auger, and it also exerts a torque force of 1500 lb on the auger. If the shaft of the auger is a solid circular rod with a diameter of 2.0 in, determine the principle stresses and the maximum shear stress at a typical point A on the surface of the shaft of the auger near the power unit.