94. Solving a chemistry problem

20c When determining vanadium by the method of additions, a sample of steel a was dissolved, the volume was adjusted to 50.0 ml. Then 20.0 ml aliquots of the solution were withdrawn into two 50 ml volumetric flasks. In one of them, a weighed portion of vanadium salt containing 0.0030 g of vanadium was added. Hydrogen peroxide was added to both flasks and the volumes were adjusted to the mark. Calculate the percentage of vanadium in steel if the following results were obtained during photometry of solutions:
a, d 0.9580
Dx 0.28
Dx st 0.48