141. Solving a chemistry problem

In standard solutions of a potassium salt with a concentration of c (K +), the electrode potentials of the potassium-selective electrode were measured relative to the silver chloride electrode:
C (K +), mol/L 1.0*10 ^-1 1.0*10 ^-2 1.0*10 ^-3 1.0*10 ^-4
E, mV 100 46.0 -7.00 -60.0
Based on these data, a calibration graph was constructed in the coordinates E - pc (K +).
A weighed portion of a sample weighing 0.2000 g, containing potassium, was dissolved in water and the volume was brought to V ml. Then the electrode potential of the potassium-selective electrode (Ex) was measured in the resulting solution:
Option 1
V, ml 100.0
Ek, mV 60.0
Calculate the mass fraction (%) of potassium in the sample.