Help me with my hw? Please. (Stoichiometry)?

1) 5.13g of a sample of hydrated sodium carbonate, Na2CO3.nH20 was dissolved in water and made up to 250cm3 in a volumetric flask. 25.0cm3 of the solution required 25.90cm3 of 0.138 mol/dm3 HCl for complete neutralization. Calculate the number of water of crystallization(n) in the carbonate.