The Figure Shows Two Point Sources of Light,A and B,that $\lambda$

Multiple Choice

The figure shows two point sources of light,A and B,that emit light waves in phase with each other.A is distant 3 $\lambda$ from point P.B is distant 5 $\lambda$ from P.( $\lambda$ is the wavelength. ) The phase difference between the waves arriving at P from A and B is

A) 0 rad.
B) $\pi$ rad.
C) 2 $\pi$ rad.
D) 3 $\pi$ rad.
E) 4 $\pi$ rad.