In a laboratory experiment, a researcher takes a cube of ammonia from a freezer set to -100.0°C and places it into a 100 g silver calorimeter containing 500 g of water. The water is initially at room temperature, 25.0°C. After some time, the system reaches thermal equilibrium, with all the water at 10.0°C. Given this information, determine the mass of the ammonia cube used in the experiment. Use specific heat capacity of ammonia (solid) = 2.09 J/g.°C, specific heat capacity of ammonia (liquid) = 4.70 J/g.°C, specific heat capacity of silver = 0.235 J/g.°C, specific heat capacity of water = 4.18 J/g.°C, and heat of fusion of ammonia = 332 J/g.