a triple effect evaporator with forward feed evaporating aqueous solution with negligible boiling point rise and containing $10wt\%$ solids to $50\%$ solids. fresh saturated steam at $1\mathrm{.}02$atm abs $($corresponding to $120C$ of temperature$)$ is used for heating in the first effect. the pressure in the vapor space of the third effect is $10cmHg.$ at given pressure, the boiling point of the solution is in the third effect is $51C.$ the feed rate $25000k\frac{g}{h}$ and temperature $21C.$ the liquid heat capacity is $4\mathrm{.}18k\frac{j}{k}g*C$ for all liquid concentrations. the heat transfer coefficients are $u1=2750,u2=1750$ and $u3=1000$kca$\frac{l}{m^{2.}}hC$

Calculate the surface area of each effect, mass flow rate of the steam, distribution of temperatures in each effect and steam economy of system.