A torque and axial loading are applied to the hollow shaft shown. Determine the minimum mid-wall radius R (in mm), assuming the torque Tis 2 KN-m, the axial load Fx is 50-kN, the length of the shaft AB is 1.2- m, the shaft's thickness t is 7 mm, and the allowable normal stress is 214 MPa. Use Coulomb's criterion (i.e., max principal stress). Also, use the following formula for the shear stress T = T/(2ta); where T is the applied torque, t is the shaft thickness, and a is the cross sectional area = 2tR. Use the same area a for your normal stress calculation. A AB T B X