20. Solving a chemistry problem

94. To build a calibration graph when determining copper in solution on a single-beam photometer, the following data were obtained:
copper content, mg/l 0.00 0.10 0.20 0.50 0.75 1.00
number of divisions I 80.0 (I0) 67.5 57.0 34.5 28.5 15.0
Build a graph in coordinates A-f (c). A portion of a sample containing copper, weighing 0.5000 g, was dissolved, transferred to a 100.0 cm3 volumetric flask, and a photometric reaction was carried out. Determine the copper content in the test sample (%) if the reading on the aperture scale is 30.4 divisions.