Wave Optics

\(\mathrm{A}\) and \(\mathrm{B}\) are two interfering sources where \(\mathrm{A}\) is ahead in phase by \(54^{\circ}\) relative to B. The observation is taken from point \(\mathrm{P}\) such that PB \(-\) PA = 2.5 \(\lambda\). Then the phase difference between the waves from A and B reaching point P is (in rad)