Values of work function (W$_0$) for a few metals are given below

Metal	Li	Na	K	Mg	Cu	Ag
W$_0$/eV	2.42	2.3	2.25	3.7	4.8	4.3

The number of metals which will show photoelectric effect when light of wavelength $400 \mathrm{~nm}$ falls on it is ___________

Given: $\mathrm{h}=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}$

$c=3 \times 10^{8} \mathrm{~ms}^{-1}$

$e=1.6 \times 10^{-19} \mathrm{C}$