54. Solving a chemistry problem

81. The molar absorption coefficient of the complex of iron with sulfosalicylic acid at a wavelength of 416 nm is 4000. Determine which sample of Fe2 (SO4) 3 • 9H2O should be dissolved in 50 ml of water so that from 5 ml of this solution after appropriate processing and dilution to 25 ml a colored solution was obtained, the optical density of which in a cuvette with a layer thickness was equal to 1.5.