From the definition of normal strain,

$\mathrm{\epsilon }=\frac{\mathrm{\delta }}{\mathrm{L}}$

the normal strain in rods $\left(2\right)$ can now be computed:

$$\begin{gathered} {\mathrm{\epsilon }}_2=\frac{{\mathrm{\delta }}_2}{{\mathrm{L}}_2}=\frac{1.8 \mathrm{mm}}{900 \mathrm{mm}} \\ =0.0020 \mathrm{mm}/\mathrm{mm} \\ =\mathbf{2}\mathbf{,}\mathbf{000}\mathbf{ }\mathbf{\mu \epsilon } \end{gathered}$$