A paramagnetic material has ${10}^{28} \mathrm{atoms} {\mathrm{m}}^{-3}$. Its magnetic susceptibility at temperature $350\mathrm{ }\mathrm{K}$ is $2.8×{10}^{-4}$. Its susceptibility at $300\mathrm{ }\mathrm{K}$ is

From Curie's law, the magnetic susceptibility is inversely proportional to the temperature, i.e.,

$\chi \propto \frac{1}{T}$

Hence, the ratio of magnetic susceptibility at different temperature $T_1=350 \mathrm{K}$ and $T_2=300 \mathrm{K}$.

$\frac{{\chi }_2}{{\chi }_1}=\frac{T_1}{T_2}$

${\chi }_2={\chi }_1\times \frac{T_1}{T_2}=2.8\times {10}^{-4}\times \frac{350}{300}$

${\chi }_2=3.267\times {10}^{-4}$.