The coefficient of elasticity normally

The stress-strain curves for brass, steel and rubber are shown in the figure. The lines $A,B$ and $C$ are for:-

To double the length of an iron wire having $0.5 {\mathrm{cm}}^2$ area of cross-section, the required force will be $\left(Y={10}^{12} \mathrm{dyne} {\mathrm{cm}}^{-2}\right)$