Q $1($c$)[5$ Marks$]$ Light of a wavelength $619$ nm falls on an aluminium surface. In aluminium photons of energy at least $4\mathrm{.}2$ eV required to remove an electron. Find: $($i$)$ The kinetic energy of the fastest photoelectron $($ii$)$ The kinetic energy of the slowest electron $($iii$)$ The stopping potential.