A single effect evaporator operates at $13k\frac{N}{m^2}.$ What will be the heating surface necessary to concentrate $1\mathrm{.}25k\frac{g}{s}$ of $10\%$ caustic soda to $41\%,$ assuming a value for overall coefficient of $1\mathrm{.}25k\frac{W}{m^2}.K,$ using steam at $390K?$ The heating surface is $1\mathrm{.}2m$ below the liquid level.

B B$.$P$.$R $=30K.$

Feed temperature $=291K.$

D Specific heat of feed $=4k\frac{J}{k}g.$ K$.$