You are a neuroengineer interested in developing better nerve stimulators for prothetic limbs, such as arms, hands or legs. You want to understnad the flow of ions across the typical nerve cell membrane during action potentials, or spikes.

Assumptions:

a) Depolrization phase: Na⁺ ions flow into the cell at a rate of 8.2 X 10¹⁵ ions/(cm²*s)
b) Duration of the Depolarization phase: 0.15 ms.
c) Repolarization phase: K⁺ ions flow out of the cell at a rate of 4.4 X 10¹⁵ ions/(cm²*s)
d) Duration of the Repolarization phase: 0.27ms
e) Size of the nerve cell membrane patch involved the action potential: 25 µm²
f) Area conversion : 1 cm² /10⁸ µm²
g) Na⁺ and K⁺ have an elementary charge of +1 , or +1.7 X 10^-19 C/ion

This change in charge does not remain for very long. What cell membrane mechanism reduces this charge imbalance over time?