139. Solving a chemistry problem

A weighed portion of silicon dioxide with a mass of m (g) was decomposed with hydrofluoric acid, and a solution of rhodamine 6G and benzene was added. Fluorescence intensity of the extract relative to the blank solution carried out under the same conditions (Ix-Io).
To build a calibration graph for a solution containing 0.05; 0.1; 0.2; 0.3; 0.4; 0.5 μg Ta2O5, added rhodamine 6G, and extracted with benzene. The fluorescence of the extracts was measured in relation to the fluorescence of the zero solution (Ix - Io): 4; eight; 16; 24; 33; 41 respectively.
Calculate the mass fraction (%) of tantalum in SiO2 according to the following data:
m (g) 2.356
(Ix-I0) 28