Electrons are ejected from the surface of a metal by the photoelectric effect. The maximum speed of the ejected electrons is found to be$4\mathrm{.}6$x$10^5$m$/$s when light with a wavelength of $625$nm is used.

a$)$What is the maximum kinetic energy of the ejected electrons in electronvolts $($eV$)?$

b$)$What is the work function of the metal?

c$)$What is the cutoff frequency for this metal? $($In other words, what is the lowest frequency of light that will still allow electrons to be ejected from the metal?$)$