An aqueous solution containing 15% NaOH and 0.5% NaCl is concentrated at a rate of 100 kg/min in a evaporator. The concentrated solution is then mixed with a 2000 kg of aqueous solution of NaOH solution in a mixer. At the end of I hour sample is collected from mixer and analyzed. The analysis show that 40% NaOH and 0.8574% NaCl.

 Calculate the composition of concentrate from the evaporator.