An aluminium block of mass 0.25 kg is at 150 °C. It is quickly submerged in 1.0 kg of water at 25 °C contained in a perfectly insulated vessel; the system reaches an intermediate equilibrium temperature T1. Immediately afterward, a second 1.0 kg sample of water at 25 °C is added to the same vessel, and the system settles at a final equilibrium temperature T2. Neglect any energy exchange with the vessel or surroundings. The specific heat capacities are 900 J kg⁻¹ °C⁻¹ for aluminium and 4.2×103 J kg⁻¹ °C⁻¹ for water. Determine T2.