139. Solving a chemistry problem

65. To determine the copper content in brass, a weighed portion of the last mass m g was dissolved and. after appropriate processing, the volume of the solution was brought to 50 ml. When removing the polarogram of the resulting solution, the wave height turned out to be equal to hX. Polarography of four standard copper solutions gave the following results - Table 16.
Table 16
CCu, mg / ml 0.5 1.0 1.5 2.0
h, mm 5.0 15.0 25.0 35.0