The difference in pH between the internal as well as external surfaces of the inner mitochondrial membrane is 1.4 pH units (external side acidic). If the membrane potential is 0.06V inside negative, the free energy change on transporting 1 mol of protons across the membrane from outside to inside at 298K is -13.8 kJ/mol. Explain how many protons must be transported to provide sufficient free energy for the synthesis of 1 mol of ATP assuming standard biochemical conditions?