Hi there, would you please solve it real quick, that would be helpful and appreciated. I will give you a good feedback too. Thank you.?

Two rays of light of wavelength 600 nm in air are initially in phase. They then travel through plastic layers as shown with L1 = 4.0 um, L2 = 3.5 um, n1 = 1.4, n2 = 1.6. When they later arrive at some common point with the same amplitude, is their interference fully constructive, fully destructive, intermediate but closer to fully constructive, or intermediate but closer to fully destructive? Explain. -L2 n1 L1