126. Solving a chemistry problem

37. Acetic acid solution with a volume of 1000 ml contains 0.0650 g of the dissolved preparation of riboflavin (vitamin B2). We took 10 ml of this solution, diluted it with an aqueous solution of sodium acetate to 100 ml, and measured the optical density A = 0.574 of the resulting solution on a spectrophotometer in a cuvette with an absorbing layer thickness l = 1 cm at a wavelength λ = 267 nm.
Calculate the percentage of riboflavin CI7H20N4O6 in the analyzed solution if the molar extinction coefficient of riboflavin in the measured solution at λ = 267 nm is ε = 32000 l * mol-1 * cm-1.
Answer: 99%.