A 98.2-g aluminum calorimeter contains 258 g of water. The aluminum and water are initially in thermal equilibrium at a temperature of 11°C. Two solid objects are then placed in the water. One is a 49.7-g piece of copper with a specific heat of 390 J/(kg⋅°C) and an initial temperature of 81.4°C. The other is of unknown material with a mass of 70.3 g and an initial temperature of 100°C. The entire system reaches thermal equilibrium at a temperature of 20.4°C. The specific heats of aluminum and water are 910 J/(kg⋅°C) and 4186 J/(kg⋅°C), respectively. Find the specific heat of the unknown material, in units of J/(kg⋅°C).