6. Solving a chemistry problem

9(3). To determine iron (III) in concentrated sulfuric acid in the form of sulfosalicylate, a sample is placed in a flask with a capacity of 100.0 ml, the necessary reagents are added and the mixture is made up to the mark with water. Measure the optical density at λeff. = 420 nm (ελ = 6*10^3) and cuvette thickness L cm. Calculate the weight of iron sample for analysis if the optimal density value is 0.435.
wFe(III),% 0.010
L.cm 1.0