Two general chemistry students working together in the lab weigh out 0.832 g of CaCl₂ ∙ 2 H₂O into a crucible. After heating the sample for a short time and allowing the crucible to cool, the students determine that the sample has a mass of 0.739 g. They then do a quick calculation. On the basis of this calculation, what should they do next?

(a) Congratulate themselves on a job well done.
(b) Assume the bottle of CaCl₂ ∙ 2 H₂O was mislabeled; it actually contained something different.
(c) Heat the crucible again, and then reweigh it.