Hydrochloric acid $($A$)$ diffuses through a thin film of water $($B$)4\mathrm{.}0$ mm thick at $283$ K$.$ The concentration of HCl at point $1$ on one boundary of the film is $12$ wt$\%$ and on the other boundary, at point $2$ is $4$ wt$\%.$ The diffusivity of HCl in water is $2\mathrm{.}5$ x $10-9$ m$2/$s$.$ Calculate the flux of HCl considering water to be stagnant. Density of the solutions at points $1$ and $2$ are $1060\mathrm{.}7$ kg$/$m$3$ and $1020\mathrm{.}15$ kg$/$m$3$ respectively.