111. Solving a chemistry problem

In a 0.1M potassium chloride solution, D-riboflavin (С17H20N4O6) and nicotinic acid (C5H4NCOOH) have a half-wave potential E1/2 of -0.35 and -1.17V, respectively. To build calibration graphs, polarograms of standard solutions of these substances were recorded at -0.6 and -1.8 V and the diffusion current was measured:
Concentration, mol/l 0.000400 0.000600 0.000800 0.001000
I(D-riboflavin), μA 2.4 3.6 4.8 6.00
I(Nicotinic acid), μA 2.20 3.30 4.40 5.50

Calculate the concentrations (mg/ml) of D-riboflavin and nicotinic acid in the analyzed solution if the polarogram had two waves at the corresponding potentials, and the diffuse current was 5.2 and 4.8 μA