A small piece of cesium metal (φ = 1.9 eV) is kept at a distance of 20 cm

A small piece of cesium metal ( $\varphi=1.9 \mathrm{eV})$ is kept at a distance of $20 \mathrm{~cm}$ from a large metal plate with a charge density of $1.0 \times 10^{-9} \mathrm{C} \mathrm{m}^{-2}$ on the surface facing the cesium piece. A monochromatic light of wavelength $400 \mathrm{~nm}$ is incident on the cesium piece. Find the minimum and maximum kinetic energy of the photoelectrons reaching the large metal plate. Neglect any change in electric field due to the small piece of cesium present.