3. A bronze bar 3m long with a cross-sectional area of 320mm² is placed between two rigid walls as shown in the figure. At a L = 3 m temperature of -20°C, the gap A-2.5 mm. Find the temperature at which the compressive stress in the bar will be 35 MPa. Bronze has a = 18.0 x 10-6 °C-1 and E = 80 GPa. (10 pts)