JEE Advanced 2021 Physics question

In a photoemission experiment, the maximum kinetic energies of photoelectrons from metals , and are , and , respectively, and they are related by . In this experiment, the same source of monochromatic light is used for metals and while a different source of monochromatic light is used for the metal . The work functions for metals , and are 4.0 eV, 4.5 eV and 5.5 eV, respectively. The energy of the incident photon used for metal , in eV, is .