Twо circulаr pоlycаrbоnаte [E = 7.6 GPa; ν = 0.36; α = 21 ×10-6/°C] disks are shown. At an initial temperature of Ti = 22°C, the diameter of the smaller disk is D = 80 mm and the thickness of the disk is t = 9.0 mm. At a final temperature of Tf = 55°C, determine the change in thickness of the disk.