2. Solving a chemistry problem

2. A portion of methylamine CH3NH2 weighing 0.2500 g was dissolved in a volumetric flask with a capacity of 50.00 ml. Potentiometric titration of 5 ml of the resulting solution with perchloric acid in anhydrous acetic acid gave the following results:
V(HClO4), ml 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20
E, mV 431 439 450 465 486 523 550 566 575
Construct potentiometric titration curves in the coordinates E-V and ΔE / ΔV - V and calculate the molar concentration of the perchloric acid solution.