A 1.00 kg block of copper at 20.0°C is lowered into a large insulated container of liquid ammonia at its boiling point (-33.3°C). If the specific heat of copper is 387 J/kg°C and heat of vaporization of liquid ammonia is 1371 kJ/kg, determine the mass of liquid ammonia that boils away before thermal equilibrium. Assume an excessive amount of liquid ammonia is present and that the liquid ammonia does not react with the copper.