A double effect has 20 m2 for each effect and is thought to concentrate a 10 to 50% solution that enters direct current at 40C. The solution does not show an increase in its boiling point and the heat capacity is 1 kcal/kg C. The heating steam is saturated at 3 atm absolute and in the second effect a vacuum of 610 mm of Hg, referred to 760 mm of Hg, is maintained. The total heat transfer coefficients are U1 = 2200 and U2 = 1500 kcal/h m2 C. How much solution can be treated per hour in the double effect?