Two steel rods and an aluminium rod of equal length l0 and equal cross-sectional areas are joined rigidly together as shown in the figure below. All the rods are in a state of zero tension at 0 ∘C. Find the length of the system when the temperature is raised to θ. Coefficient of linear expansion of aluminium and steel are αa and αs respectively. Young's modulus of aluminium is Ya and of steel is Ys.