Can you provide a detailed step by step solution using mass transfer formulas? A cubic volume which is $1$ cm on each side is moving to the right at steady state in the $+$z direction with a molar bulk average velocity of $2$ cm$/$s$.$ In the volume there are $3$ moles of A $($MW$=2$ g$/$mol$),2$ moles of B $($MW$=3$ g$/$mol$)$ and $4$ moles of C $($MW$=4$ g$/$mol$).$ Molecule A diffuses in $+$z direction with a diffusion rate of $2$ mol$/$s and molecule B diffuses in the opposite direction with a diffusion rate of $2$ mol$/$s$.$

Molecule C is under the effect of convective flow only. Calculate:

a$)$ the local velocity of each component

b$)$ the mass average velocity of the bulk