In an experiment with Lummer Gehrecke plate, the two coherent beams...

In an experiment with Lummer Gehrecke plate, the two coherent beams of light, caused by multiple reflections inside the transparent plate of refractive index $\mu=1.54$, reach the points P and $Q$ on the screen. The net path difference between the two beams reaching either at P or Q is $\Delta x=5000 \mathrm{~nm}$. Which of the wavelengths in the visible range ( $\lambda=390 \mathrm{~nm}$ to $\lambda=780 \mathrm{~nm}$ ) is/are most likely to produce a constructive interference (a maximum) at the point P as well as at Q on the screen?