A beam of the cross section shown is made of a steel that is assumed to be elastoplastic with E= 200 GPa and ay= 236 MPa. The bending is about the z axis. A bending couple is applied to the beam causing plastic zones 30 mm thick to develop at the top and bottom of the beam. The couple is then removed. NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. 60 mm- 90 mm Problem 04.091.a - Residual stress in a rectangular elastoplastic beam Determine the residual stress at y=45 mm. The residual stress is MPa.