A student drops two metallic objects into a 120 g steel container holding 150 g of water at 25°C. One object is a 170 g cube of copper that is initially at 85°C, and the other is a chunk of aluminum that is initially at 5.0°C. To the surprise of the student, the water reaches a final temperature of 25°C, exactly where it started. What is the mass of the aluminum chunk?