There is gap between the three copper bars and the rigid slab that is supported by two aluminum bars at $25C=0\mathrm{.}10mm.$ For each copper bar, $A=400m{m}^2,E=120$GPa, and $=16\mathrm{.}8\frac{m}{m*C}.$ For the aluminum bar, $A=500m{m}^2,E=70$GPa, and $=23\mathrm{.}1\frac{m}{m*C}.$ Neglecting the mass of the slab and when the temperature in the assembly is increased to $50C.$

a$.$ Determine the stress in the aluminum.

b$.$ Determine the stress in the copper.