Both the capacitors shown in figure are made of square plates of edges a.

Both the capacitors shown in figure are made of square plates of edges a. The separations between the plates of the capacitors are $d_{1}$ and $d_{2}$ as shown in the figure. A potential difference $V$ is applied between the point a and $b$. An electron is projected between the plates of the upper capacitor along the central line. With what minimum speed should the electron be projected so that it does not collide with any plate? Consider only the electric forces.