Stoichiometry problem?

a student weighed a crucible and found it to weigh 12 grams. 20 grams of copper II ? Hydrate (CuSO4 - ? H20) was placed in the crucible and heated for 10 minutes. After 10 minutes the crucible and the andhydrate were found to weigh 21.76 grams. How many water molecules are attached to the anhydrate magnesium sulfate.