28. Solving a chemistry problem

62a. The determination of iron (II) was carried out by a photoelectrocolorimetric method based on the reaction of formation in aqueous solutions at pH 4 - 6 of an orange-red complex of iron (II) with 1,10-phenanthroline. The method of one standard was applied.
Test and standard solutions containing iron(II) complex with 1,10-phenanthroline were prepared in two volumetric flasks with a capacity of 25 ml. To do this, an aliquot portion of the analyzed solution with an unknown concentration Cx of iron (II) with a volume Vx was placed in one flask, and an aliquot portion of a standard solution with a precisely known concentration Cst of iron (II) with a volume Vst was placed in another flask; ¬ ric reaction and brought the volume of solutions to the mark with water.
The optical density Ax and Ast, respectively, of the studied and reference solutions were measured on an FEK-N-57 photoelectrocolorimeter with a light filter having a maximum light transmission at 508 nm, in a cuvette with an absorbing layer thickness of 1.00 cm. A solution containing all reagents was used as a reference solution. necessary for carrying out the photometric reaction, except for iron (II).
Using the data below, calculate the content (mg) of iron (II) in 100 ml of the analyzed solution.
Vx, ml Cst, μg/ml Vst, ml Ax Ast
10.00 1.00 2.00 0.20 0.16