A bar that is given to be 2 m in height (long) is bent and then stress relieved. The radius of curvature to the neutral axis is 0.49 m. The bar is 25 mm thick and is made of an elastic, perfectly plastic material with Y = 600 MPa and E= 210 GPa. Find and calculate the length to which this bar should be stretched so that, after unloading, it will become and stay straight.