Regarding the N a$^+/$K$^+$ antiporter that is responsible for hydrolyzing more than half the ATP molecules in a neuron: what is the direction this protein pumps potassium ions? Select one: a$.$ from the cytoplasm to the extracellular fluid b$.$ from the cytoplasm to the nucleus c$.$ from the extracellular fluid to the cytoplasm Od$.$ from the late endosome lumen to the peroxisome e$.$ from the endoplasmic reticulum $($ER$)$ lumen to the early endosome lumen