A pair of evaporators will be arranged in series to remove water from a salt solution $($i$.$e$,$ the salt solution that exits the first evaporator will be the feed to the second evaporator$).$ The first evaporator will be operated at conditions sufficient to evaporate water at a rate of $9$kmo$\frac{l}{h}.$ The second evaporator will be operated at conditions sufficient to evaporate water at a rate of $4\mathrm{.}5$kmo$\frac{l}{h}.$ You may assume that no salt exits either unit via evaporation. The salt solution that exits the first evaporator $($i$.$e$.,$ the feed to the second evaporator$)$ flows at a rate of $63\mathrm{.}5k\frac{g}{h}$ and contains a $\frac{50}{50}$ mixture $($by mass$)$ of water and salt.

b$)$ A correctly drawn flow chart will include $3$ system boundaries$-$ the overall, evaporator $1,$ and evaporator $2.$ Perform a degree of freedom analysis for each system boundary and specify an order in which the problem could be solved to determine all unknowns.