Solving a problem in chemistry section 10 point 43

43. The alloy of copper, lead, iron and zinc weighing 6.49 g was treated with a solution of nitric acid. To this solution was surged excess sulfuric acid solution, thus formed precipitate weight was 3.03 g in the remaining solution was passed hydrogen sulphide, resulting in a precipitate weight was 3.84 in the remaining solution was added concentrated ammonia solution, while precipitate mass 1 07 was calculated mass fractions of metal in the mixture.