\(\frac{\chi _{1}}{\chi _{2}}=\frac{T_{2}}{T_{1}}\)
\(\Rightarrow \chi _{2}=\frac{T_{1}}{T_{2}} \times \chi _{1}=\frac{350}{300} \times 2.8 \times 10^{-4}\)
\(=3.267 \times 10^{-4}\)