A 0.4672 g sample of pewter (containing tin, lead, copper, and zinc) was dissolved in acid. The precipitate SnO2·4H2O was removed by filtration. The resulting filtrate and washings were diluted to a total volume of 250.0 mL. A 15.00 mL aliquot was buffered and titration of the lead, copper, and zinc required 35.78 mL 0.001500 M EDTA. Thiosulfate was used to mask the copper in a 20.00 mL aliquot. Titration of the lead and zinc in this aliquot required 34.06 mL of the EDTA solution. Finally, cyanide was used to mask the copper and the zinc in a 25.00 mL aliquot. Titration of the lead required 26.68 mL of the EDTA solution. Determine the composition by mass of the pewter sample