Find max stress sigma_theta. The cylinder is hollow in the center, one layer of steel inside and a layer of brass outside. a is radius of hollow portion, b is radius of steel and c is radius of brass. deformation=0.02mm, a=40mm, b=80mm, c= 140 mm Ebrass=110gpa, nu-brass=0.32. E-steel=200gpa, nu-steel=0.28.