111. Solving a chemistry problem

A portion of the alloy, 2.1574 g, was dissolved and, after appropriate treatment, the volume of the solution was adjusted to 100.0 ml. Determine the percentage of silver in the alloy, if the following results were obtained during potentiometric titration of 25.0 ml of the prepared solution with 0.1250 N sodium chloride solution:
V,NaCl, ml 16.0 18.0 19.0 19.5 19.9 20.0 20.1 20.5 21.0
Е,mB 689 670 652 634 594 518 441 401 383