30. Solving a chemistry problem

14. Nitrobenzene, contained in 210 mg of a mixture of organic substances, was reduced on a mercury cathode to phenylhydroxylamine at a constant potential of -0.96 V (relative to the NCE). The analyzed mixture was dissolved in 100 ml of methanol; the reaction was completed after electrolysis for 30 minutes. The coulometer showed that 26.74 C was spent on restoration. Calculate the percentage of nitrobenzene in the mixture.