A rigid tank of 2.265 m3 capacity contains 1896 kg of saturated liquid water at 494.15 K (221°C). This amount of liquid almost completely fills the tank, the small remaining volume being occupied by saturated-vapor steam. Since a bit more vapor space in the tank is wanted, a valve at the top of the tank is opened, and saturated-vapor steam is vented to the atmosphere until the temperature in the tank falls to 488.15 K (215°C). Assuming no heat transfer to the contents of the tank, determine the mass of steam vented.