How much longer is a $150 \, \mathrm{km}$ railway in a warm summer ( $25^\circ \mathrm{C}$ ) than a cold winter ( $-20^\circ \mathrm{C}$ )? It is known that a one-meter iron rod lengthens by the equation $1 \cdot 10^{-7} \, \mathrm{m}$ when the temperature increases by one degree.

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