Answer
$(a)$ No If $V_{m}$. were set by permeability to (primary) $K^{+}$, the Nernst equation would predict a $V_{m}$ of $-$90 mV, not the observed $-$95 mV, So some other conductance must contribute to $V_{m}$.
$(b)$ Chloride ion is probably the determinant of $V_{m}$; the predicted $E_{Cl^{-}}$ is $-$94 mV.
Work Step by Step
$(a)$ No If $V_{m}$. were set by permeability to (primary) $K^{+}$, the Nernst equation would predict a $V_{m}$ of $-$90 mV, not the observed $-$95 mV, So some other conductance must contribute to $V_{m}$.
$(b)$ Chloride ion is probably the determinant of $V_{m}$; the predicted $E_{Cl^{-}}$ is $-$94 mV.
