A single effect evaporator concentrates 1.1 kg s of NaOH solution from 8% to 30%.Feed solution is at 60 degrees C with a specific heat capacity of 4.2 kJ kg K.A 30% solution of NaOH has a b.p elevation of 30 degrees C.Heating steam at 1.4 bars and pressure in separator is 0.1 bara. Condensate is collected at rate of 1 kg s at its condensing temp. Overall heat transfer coefficient is 3000 W m2 K. Calculate the heating surface required in calandra in m2 and the economy of the evaporator.