Elongation of a steel bridge

A bridge has a steel structure ($\alpha =1.2\cdot 10^{-5}{\mathrm{K}}^{-1}$) $200\mathrm{m}$ long at a temperature of $-10{}^{\circ }\mathrm{C}$. Compute the elongation of the structure when the temperature rises to $40{}^{\circ }\mathrm{C}$.