Starting with the expression for concentration of species A and $B$ in the evaporation in a column

$[$Arnold Cell example, Example $1]$ we did in class, show that the flux for $B$ is zero even though the

concentration of $B$ varies with $z$ and therefore will contribute to the diffusive flux. Compare the

diffusive and convective fluxes for $B$ and write a short justification for why the overall flux for $B$ turns

out to be zero.