Record your observation about the landforms that remain after the wax has stopped flowing

This is a mixture that has the same composition throughout.

0.09 moles of sodium sulfate in 12 ml of solution

In the millikan oil drop experiment they determined that every drop had a charge which was a while number multiple of -1.60x10^-19. if a drop has a total charge of -9.60x10^-19 then how many excess electrons are contained within the drop?