Physics numerical problem class 12th (Ch-Electrostatics). Need Help!!?

A positively charged oil droplet remains stationary in the electric field between two horizontal plates separated by a distance of 1cm.If the charge on the drop is 9.6*10^-16 C and the mass of the droplet is 10^-11g.What is the potential difference between the plates? Now if the polarity is reversed, what is the instantaneous acceleration of the droplet?