A single-effect evaporator is used to concentrate 60000 kg h^-1 of a 40 wt % NaOH solution which is fed to the evaporator at 40°C. The concentrated liquid is a 55 wt % NaOH solution. Saturated steam at 3 atm is available for heating. The vapor space in the evaporator is at a pressure of 10 kPa. The overall heat transfer coefficient is 2000 W m^-2 K^-1. Determine:

a) The amount of vapor produced.

 b) The area required for the evaporator. Include clearly values of relevant properties.

c) The economy.