Values of work function $\left({\mathrm{W}}_0\right)$ for a few metals are given below 

The number of metals which will show photoelectric effect when light of wavelength 400nm falls on it is __________
Given :  $\mathrm{h}=6.6\times {10}^{-34}\mathrm{J}\mathrm{s}$
$$\begin{gathered} \mathrm{c}=3\times {10}^8\text{m\hspace{0.17em}}{\mathrm{s}}^{-1} \\ \mathrm{e}=1.6\times {10}^{-19}\mathrm{C} \end{gathered}$$