2.(30分)A trimetallic bar is uniformly compressed by an axial force P = 12 kN applied througha rigid end plate (see figure). The bar consists of a circular steel core surrounded bybrass and copper tubes. The steel core has diameter 10 mm, the brass tube hasouter diameter 15 mm, and the copper tube has outer diameter 20 mm. The moduli ofelasticity for steel, brass and copper are 210, 100, and 120 GPa, respectively.