An aqueous food solution at a temperature of 18 °C contains 6% solids by mass and is to be concentrated to 24 % solids in a single effect evaporator. The evaporator has a total heat transfer surface area of 30 m2, uses steam at 300 kPa and operates under a vacuum of 79.3 kPa. Previous operating experience with these conditions suggests an overall heat transfer coefficient of 2,200 W m-2K-1. Determine the mass flow rate of steam required and the evaporator economy.