Four identical hollow cylindrical columns of mild steel support a big structure of mass $50 \times 10^3 \mathrm{~kg}$, The inner and outer radii of each column are 50 cm and 100 cm respectively. Assuming uniform local distribution, calculate the compression strain of each column. [Use $Y=2.0 \times 10^{11} \mathrm{~Pa}, g=9.8 \mathrm{~m} / \mathrm{s}^2$ ]