When electromagnetic radiation of wavelength 300 nm falls on the surface of a metal, electrons are emitted with the kinetic energy of ${\text{1.68×10}}^{\text{5}}{\text{\hspace{0.17em}J\hspace{0.17em}mol}}^{\text{-1}}$. What is the minimum energy needed to remove an electron from the metal ?  
${\text{(h=6.626×10}}^{\text{-34}}{\text{Js,\hspace{0.17em}c=3×10}}^{\text{8}}{\text{\hspace{0.17em}ms}}^{\text{-1}}\text{,}$
${\text{N}}_A{\text{=6.022×10}}^{\text{23}}{\text{\hspace{0.17em}mol}}^{\text{-1}}\text{)}$