An alloy weighing 0.6470 g containing Ni, Fe and Cr was dissolved and transferred to a volumetric flask with a capacity of 250 ml.
1) 50.0 ml of a 0.052 M EDTA solution was mixed with an equal volume of the sample, and the excess EDTA was titrated using 5.11 ml of a 0.062 M standard copper solution (three metal ions were titrated).
2) In the second 50.0 ml aliquot, Cr was masked, and 36.2 ml of the same EDTA solution was used for the titration of Fe and Ni.
3) In the third aliquot, 50.0 ml, Fe and Cr were masked, and 25.9 ml of EDTA solution was used for Ni titration. Determine the mass fractions of Fe, Ni Cr in the sample.

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