Two metal plates $(A, B)$ are kept horizontally with separation of $\left(\frac{12}{\pi}\right) \mathrm{cm}$, with plate $A$ on the top. An atomizer jet sprays oil (density $1.5 \mathrm{~g} / \mathrm{cm}^3$ ) droplets of radius 1 mm horizontally. All oil droplets carry a charge 5 nC . The potentials $V_A$ and $V_B$ are required on plates A and B respectively in order to ensure the droplets do not descend. The values of $V_A$ and $V_B$ are $\_\_\_\_$ . (Neglect the air resistance to the droplets and take $\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ )