111. Solving a chemistry problem

115. By chromatography on paper impregnated with potassium hexacyanoferrate(II), the following spot areas were obtained depending on the concentration of standard solutions of copper(II):
C µg/0.2 cm3 0.12 0.30 0.45 0.70 0.90
Spots, mm2 14 26.3 35 51.2 66.5

When analyzing cottage cheese, 50.00 g of it was ashed, the ash was dissolved in 100 cm3 of acid, and 0.2 cm3 of the resulting solution was applied to chromatographic paper with a pipette. After chromatographic separation, the spot area for copper hexacyanoferrate(II) was determined to be 40.4 mm2. Calculate the copper content of cottage cheese (mg/kg).