When a metal surface is illuminated by a light of wavelength $400\;nm$ and $250\; nm$. The maximum velocities of the photo electrons ejected are $v$ and $2v$ respectively. The work function of the metal is : (h = Planck's constant, c = velocity of light in air )
( A ) $1.5\; hc \times 10^6 J$
( B ) $hc \times 10^6 J$
( C ) $0.5\; hc \times 10^6 J$
( D ) $2\; hc \times 10^6 J$