Atomic Structure: JEE Main 2023 Chemistry question

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: $\mathrm{h}=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}$ $c=3 \times 10^{8} \mathrm{~ms}^{-1}$ $e=1.6 \times 10^{-19} \mathrm{C}$