138. Solving a chemistry problem

A weighed portion of a natural product weighing 1.050 g was dissolved in 100 cm3 and 0.05 cm3 of the solution was applied to paper. After chromatographic separation, the resulting spot of ribose-1,5-diphosphate was cut out, fused with KOH and K2S2O8, after dissolution of the melt, phosphorus was determined photometrically, obtaining the optical density Arib = 0.790. A solution containing 20 μg / cm3 of phosphorus was prepared from a standard phosphate solution and its optical density ATP = 0.950 was measured. Determine the mass fraction of ribose * 1,5-diphosphate (%). (M (C5H12O11P2) = 310) in a natural product.