A student cut a 5.30 g magnesium ribbon into small pieces and then began to heat it in a 16.30 g crucible. Over time, the magnesium ignited and burned to form a white, grayish and powdery substance. After the crucible cooled, the student measured the mass of the crucible that contained the powder and found it to be 24.80 g. What was the mass of the resulting oxide?

5.30 g
8.50 g
12.50 g
24.80 g
cannot be determined from this information