90. Solving a chemistry problem

4. In the photocolorimetric determination of iron ions with sulfosalicylic acid, a number of solutions were prepared from a standard solution with an iron content of 10 mg/cm3 by dilution in volumetric flasks with a capacity of 50 cm3 and their optical density was measured:
Vst. solution, cm3 1.0 2.0 3.0 4.0 5.0
A 0.12 0.25 0.37 0.50 0.62
What is the molar concentration of a ferric chloride control solution if its optical density, measured under the same conditions, is 0.48?