A clean iron surface is illuminated by ultraviolet light. No photoelectrons are ejected until the wavelength of

Question:

A clean iron surface is illuminated by ultraviolet light. No photoelectrons are ejected until the wavelength of the incident UV light falls below 288 nm.
(a) What is the work function (in electron-volts) of the metal?
(b) What is the maximum kinetic energy for electrons ejected by incident light of wavelength 140 nm?