(25 points) Referring to the diagram below, and knowing that $\alpha_A = 15.2 \times 10^{-6}$/°C and $\alpha_B = 16.9 \times 10^{-6}$/°C, $R_A = 1$m, $R_B = 2$m, $E_A = 51$ GPa, $E_B = 86$ GPa, determine:
A.) The total change in length due to increase in temperature from 273 K to 468 K, assuming no constraints are present. (7 points)
B.) The reactive forces at A and B if the gap between point A and the wall is 10 mm. (7 points)
C.) The change in individual lengths of the brass and aluminum bar, again assuming a gap of 10 mm. (11 points)
D.) (extra credit). Now imagine a spring of spring constant $k_l = 11.2 \times 10^{10}$ N/m is present between the point A and the wall. How much would it deflect? (5 points) (Hint: Calculate the force generated by thermal expansion)
