Evaluate the diffusion coefficient of methane in air at $25C$ and atmospheric pressure.

a$)$ Using the Hirschfelder et al$.$ equation.

b$)$ Answer without Hirschfelder et al$.$ equation: What would be the diffusion coefficient if the

temperature were doubled, and pressure were increased by $50\%.$

c$)$ Repeat part a by using Fuller$-$Schettler$-$Giddings correlation.