Calculate the stresses in the rod and tube when the temperature

Question

A steel tube 2.5 cm external diameter and 1.8 cm internal diameter enclose a copper rod 1.6 cm diameter to which it is rigidly joined at each end. If, at a temperature of 20^oC there is no longitudinal stress, calculate the stresses in the rod and tube when the temperature is raised to 210^oC. Given: E_s = 210 GPa and $\alpha _{s}$ = 12$\times$10^–6/^oC

         E_s = 100 GPa and a_C = 20 $\times$10^–6/^oC