Ultraviolet radiation of 6.2 eV falls on an aluminium surface (work function 4.2 eV). The kinetic energy (in joule) of the fastest electron emitted is :

A. 3.2×10⁻²¹
B. 1.6×10⁻¹⁷
C. 3.2×10⁻¹⁹
D. 3.2×10⁻¹⁵