Each copper (II) sulfate unit is associated with five water molecules in crystalline copper (II) sulfate pentahydrate. When this compound is heated in air above 100 °C, it loses the water molecules and the blue color:
CuSO4·5H2O → CuSO4 + 5H2O
If 9.60 g of CuSO4 are left after heating 15.01 g of the blue compound, calculate the number of moles of water originally present in the compound.