16. Solving a chemistry problem

3. In 2 volumetric flasks per 100 ml, 20 ml of waste water were placed. 10 ml of CuSO4 standard solution (ТCu=0.0010000) was added to one flask. In both volumetric flasks were introduced solutions of ammonia, rubeanic acid and diluted to the mark with water. When photometry solutions received optical densities Ah =0.28 and Ah St=0.42. Determine the concentration of copper in waste water, g/l.