A circular steel bar ABC (E = 200 GPa) has cross-sectional area A1 from A to B and cross-sectional area A2 from B to C (see figure). The bar is supported rigidly at end A and is subjected to a load P equal to 40 kN at end C. A circular steel collar BD having cross-sectional area A3 supports the bar at B. The collar fits snugly at B and D when there is no load.
Determine the elongation δAC of the bar due to the load P. (Assume L1 = 2L3 = 250 mm, L2 = 225 mm, A1 = 2A3 = 960 mm2, and A2 = 300 mm2.)

La3 A2