The yield stress of a tension specimen machined from a 0.5 m wide by 0.6 cm thick copper sheet is 145 MPa. The sheet is rolled further in the plane of the sheet with an applied tensile force of 0.22 MN. What roll pressure is needed to just cause yielding? Ignore friction between the metal and the rolls. For rolling, deformation occurs by plane-strain in which there is no increase in the width of the sheet