Liquid air $(79$ mol$\%N_2$ and $21$mol$\%O_2)$ is separated in a distillation column, giving an overhead flow $(99$ mol$\%N_2$ and $1$mol$\%O_2,$ rectification section$)$ and a bottom flow and $40$mol$\%O_2,$ depletion section$).$ Both streams feed a second distillation column giving a top product with $98$mol$\%$ of $N_2$ and $2$ molar $\%$ of $O_2$ and a bottom product with $1\mathrm{.}5$molar$\%$ of $N_2$ and $98\mathrm{.}5$molar$\%$ of $O_2.$ For a first column bottom flow of $180$kmo$\frac{l}{h}$ :

a$)$ Make a flow chart that represents the situation.

b$)$ Calculate all remaining flows.