100. Solving a chemistry problem

2. To prepare standard solutions of titanium (IV), a certain volume of a solution containing 0.20 mg / ml of titanium (IV) was placed in volumetric flasks with a capacity of 50 ml, hydrogen peroxide was added and brought to the mark. We measured the optical density of the obtained titanium (IV) peroxide complexes at λ = 400 nm:
V, ml 0.50 1.00 1.40 1.60 1.70
A 0.13 0.44 0.76 0.90 1.04
From a sample of steel weighing 0.3000 g, after appropriate processing, 100 ml of a solution was prepared, 10 ml were taken and placed in a flask with a capacity of 50 ml, hydrogen peroxide was added and brought to the mark. The optical density of the solution at λ = 400 nm is 0.61. Calculate the mass fraction of titanium in steel.
Answer: 0.8%.