The Figure Shows Two Point Sources of Light, a and B

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 3λ from point P. B is distant 5λ from P. (λ is the wavelength.) The phase difference between the waves arriving at P from A and B is

A) 0 rad.
B) π rad.
C) 2π rad.
D) 3π rad.
E) 4π rad.