A single effect evaporator is to concentrate $10000k\frac{g}{h}$ of $20\%$ solution o sodium hydroxide to $50\%$ solids. Feed temperature is $38C$ and boiling point o the solution in the evaporator is $92C.$ Enthalpy of feed and thick liquor and vapour are respectively $128k\frac{J}{k}g,515k\frac{J}{k}g$ and $2200k\frac{J}{k}g.$ Condensatiol temperature of steam is $126C.$ If the heat of vaporization of steam at th existing condition is $2187k\frac{J}{k}g$ and overall coefficient is $1\mathrm{.}4k\frac{W}{m^{20}}C$ estimate $($i$)$ the amount of steam consumed $($ii$)$ economy and $($iii$)$ heating surface required