A steel rail with a cross-sectional area of $40\ \text{cm}^2$ is held between two rigid supports, so that it cannot get longer. Its temperature rises by $30\ \text{K}$. For steel, Young's modulus is $2.0 \times 10^{11}\ \text{N/m}^2$ and the coefficient of linear expansion is $1.2 \times 10^{-5}\ \text{K}^{-1}$. The force that the rail exerts on each support is