A stretched wire of a material whose young's modulus $$Y=2 \times 10^{11} ~\mathrm{Nm}^{-2}$$ has poisson's ratio 0.25 . Its lateral strain $$\varepsilon_l=10^{-3}$$. The elastic energy density of the wire is

A metallic rod breaks when strain produced is $$0.2 \%$$. The Young's modulus of the material of the $$\operatorname{rod} 7 \times 10^9 \mathrm{~N} / \mathrm{m}^2$$. The area of crosssection to support a load of $$10^4 \mathrm{~N}$$ is