112. Solving a chemistry problem

Equal volumes (20 cm3) of waste water containing copper were poured into two volumetric flasks per 100 cm3. The required amounts of ammonia and a solution of rubeanic acid were also introduced there. 10 cm3 of a standard solution of CuSO4 (Tcuso4/cu=0.001) was added to one of the flasks, the contents of two flasks were brought to the mark. After filtration, the solutions were photometered, obtaining the values of optical density Dx=0.28 and Dx st=0.43. Determine the concentration of copper in wastewater (g/dm3).