A steel rod of 20 mm diameter passes centrally through a copper tube of 50 mm external diameter and 40 mm internal diameter. The tube is closed at each end by rigid plates of negligible thickness. The nuts are tightened lightly on the projecting parts of the rod. If the temperature of the assembly is raised by 50oC, Find the stress developed in copper and steel. Take E for steel and copper as 200 GN/m2 and 100 GN/m2 and α for steel and copper as 12 x 10 -6/ oC and 18 x 10 -6 per oC .