111. Solving a chemistry problem

3.1 To build a calibration graph, we dissolved identical weights of four standard samples of steel containing chromium, took their polarograms and measured the height of the polarographic wave:
Sample 1 2 3 4
ωCr, % 0.30 0.42 0.96 1.40
h, mm 6.0 8.4 19.4 28.0
Determine the mass fraction (%) of chromium in the analyzed sample, if during polarography of a solution obtained under similar conditions, the height of the polarographic wave turned out to be hx = 22.00 mm.