A femur with a cortical shell thickness of 2.0 mm is force fit with a stem of 8.0 mm radius. Material property of the stem is E = 127.0 GPa, Poissons ratio= 0.33. Material property of the cortical shell is E= 12.0 GPa, Poissons ratio = 0.25. If the maximum allowable stress in the cortical shell is 15 MPa, determine what interference fit between the stem and the cortical shell should be given?