28. Solving a chemistry problem

3. To construct a calibration graph for determining cadmium, we used a standard solution of cadmium salt C(1/2Cd2+)=1*10-4 mol*l-1. Aliquots of this solution Vst (1.0; 2.0; 3.0; 4.0; 5.0; 6.0 ml) were diluted with background in the cell to 25.0 ml and polarographed. The following data was obtained:
Vst, ml 1.0 2.0 3.0 4.0 5.0 6.0
h, mm 9.0 16.0 26.5 35.0 41.0 54.0
A weighed portion m (g) of the alloy containing cadmium was dissolved in nitric acid, the acid was removed by evaporation, and the residue was diluted to a volume V (ml). A 5.0 ml aliquot was introduced into the cell and the volume was adjusted to 25.0 ml using background. When polarographing under the same conditions as standard solutions, the following data were obtained:
option m, g V, ml h, mm
3 0.500 100.0 22.5
Calculate the mass fraction w (%) of cadmium in a sample of the alloy.