Question (4): A plastic bar ACB having two different solid circular cross sections is held between rigid supports as shown in the figure. The diameters in the left- and right-hand parts are 50mm and 75mm, respectively. The corresponding lengths are 225mm and 300mm, Also, the modulus of elasticity E is 6.0GPa, and the coefficient of thermal expansion is 100106/C. The bar is subjected to a uniform temperature increase of 30C.Calculate the following quantities: (1) the compressive force N in the bar; (2) the maximum compressive stress c; and (3) the displacement c of point C