28. Solving a chemistry problem

40. The content of four foreign impurities in the lamivudine drug substance was determined using HPLC by the method of internal normalization. After processing the chromatograms, the areas of the peaks of the main substance - lamivudine and impurities were found to be equal (in relative units): lamivudine - 49; 2R- carboxylic acid - 0.50; salicylic acid - 0.25; cytosine -0.15; unidentified impurity - 0.10.
Calculate the percentage of the main substance and all impurities in the preparation.