Field from the equipotential surfaces

In a region with a uniform field the equipotential surfaces are parallel planes; two consecutive planes are $5.0\mathrm{mm}$ apart and their potentials differ by $20\mathrm{V}$. Compute the magnitude of the field and the work done by the field on an electron that goes from the surface at $10\mathrm{V}$ to the surface at $50\mathrm{V}$.