90. Solving a chemistry problem

2.1 For analysis, 100 cm3 of milk was ashed and the resulting ash was dissolved in 10 cm3 of hydrochloric acid. The resulting solution was transferred to a volumetric flask with a capacity of 100 cm3 and brought to the mark with a background electrolyte. Then a standard solution was prepared containing 5 mg of copper per 100 cm3. With sequential polarography of the obtained solutions, the wave heights were 16.0 and 26.5 mm, respectively. Calculate the content of copper in milk (in mg/dm3).