19. Solving a chemistry problem

271. To determine the copper content in brass, a sample of the latter a = 0.0690 g was dissolved and, after appropriate processing, the volume of the solution was brought to 50 ml. When taking the polarogram of the obtained solution, the wave height was equal to hх = 11 mm. Polarography of four standard copper solutions yielded the following results:
ССu•10–3, g/ml 0.5 1.0 1.5 2.0
h, mm 2.5 15.0 25.0 35.0
Build a calibration graph and determine the percentage of copper in the analyzed sample.