An electron enters the space between the plates of a charged capacitor as shown. The charge density on the plate is $\sigma$. The electric intensity in the space between the plates is $E$. A uniform magnetic field $B$ also exists in that space, perpendicular to the direction of $E$. The electron moves perpendicular to both $\vec{E}$ and $\vec{B}$ without any change in direction. The time taken by the electron to travel a distance $l$ in that space is ………….