The photoelectric effect for five metals

Five metals have different work functions. You will find the photon energy of a light, the greatest kinetic energy it gives each metal, and which metals give electrons at all. Then the program draws the result.

The idea. $E = \dfrac{1240}{\lambda}$ eV with $\lambda$ in nm, and $KE_{\max} = E - W$, or $0$ when $E \leq W$.

Your tasks.

1. In photon, return the photon energy in eV.
2. In ke_max, return the greatest kinetic energy, never below $0$.
3. Fill freed with the metals that give electrons at $400\ \text{nm}$.