Answer
The rays are exactly out of phase.
Work Step by Step
We can find the extra distance traveled by the upper ray:
$d = 150~nm+150~nm = 300~nm$
The path length difference is $~~300~nm$
Both rays reflect once from the glass surface, so any phase difference will be caused by the difference in path length.
If the path length difference is $(m+\frac{1}{2})~\lambda,$ where $m$ is an integer, then the rays will be exactly out of phase.
Note that the path length difference is $\frac{\lambda}{2}$
Therefore, the rays are exactly out of phase.
