Knowing that a 0.5-mm gap exists when the temperature is 208C, determine (a) the temperature at which the normal stress in the aluminum bar will be equal to -90 MPa, (b) the corresponding exact length of the aluminum bar. Bronze: A= 1500mm^2 / E = 105 Gpa / alpha = 21.6*10^-6 Al : A=1800 mm^2 / E= 73Gpa / alpha = 23.2*10^-6