You have constructed a perfect 1D infinite square well potential in the lab and you have an electron in the ground state in this well. The width (W) of the well is tunable. You wish to study the transition of the electron from the ground (n=1) state to the third excited state (n=3) state. You will cause this transition using a laser which emits photons which each carry an energy Ep. Write an expression for the width (W) of the square well that you need to cause the n=1 to n=3 transition with the given laser source.