\(\tau=\frac{\lambda}{\mathrm{v}}=\frac{1}{\sqrt{2} \pi \mathrm{n}_{\mathrm{v}} \mathrm{d}^{2} \mathrm{v}}=\frac{1}{\sqrt{2} \pi \mathrm{n}_{\mathrm{v}} \mathrm{d}^{2}} \sqrt{\frac{\mathrm{M}}{3 \mathrm{RT}}}\)

\(\frac{\tau_{1}}{\tau_{2}}=\sqrt{\frac{M_{1}}{M_{2}}} \frac{d_{2}^{2}}{d_{1}^{2}}\)

\(=\sqrt{\frac{40}{140}} \frac{(0.1)^{2}}{(0.07)^{2}}\)

\(=1.09\)