6. Solving a chemistry problem

2. In a volumetric flask with a capacity of 100 cm3, 0.5400 g of NiSO4 * 7H2O is dissolved. To 20.00 cm3 of this solution was added 50.00 cm3 of 0.0100 EDTA solution. For titration of the EDTA residue, 20.8 cm3 of a 0.0114 M zinc sulfate solution were used. Calculate the mass fraction of nickel in the sample.