145. Solving a chemistry problem

27-3. A weighed portion of ore of mass m g was dissolved and, after appropriate treatment, Fe2 + ions were titrated with a solution of potassium permanganate using the photometric method. Construct the titration curve and calculate the mass fraction (%) of iron in the sample according to the following measurement results:
m = 0.9987
Conc KMnO4 T (KMnO4 / Fe) = 0.005544
Opt. density of the solution after adding KMnO4, V (KMnO4), ml:
10 12 14 16 18 20
0.02 0.02 0.075 0.140 0.2 0, 265