139. Solving a chemistry problem

For the nephelometric determination of sulfur in coal, 0.0100 M H2SO4 was used as a standard. At the same time, 2.50 ml of it was diluted to 1000.0 ml, BaSO4 suspensions were prepared from V ml of the resulting solution in a flask with a capacity of 100.0 ml, and after bringing to the mark, the apparent optical density was measured. Based on the data obtained, a calibration graph was built:
V, ml 20.0 15.0 12.0 8.0 4.0 2.0
Akazh 0.210 0.330 0.420 0.600 0.800 0.920
From a sample of coal with a mass of m g, 100.0 ml of a solution was prepared, 20.0 ml of it was placed in a volumetric flask with a capacity of 250.0 ml, a suspension of BaSO4 was prepared and brought to the mark. Determine the mass fraction (%) of sulfur in coal, if the apparent optical density was:
Option 1
m, g = 1.832
Acaj = 0.69