An Observer Stands 3 M from Speaker a and 4 $\frac{\pi}{2}$

Multiple Choice

An observer stands 3 m from speaker A and 4 m from speaker B. Both speakers, oscillating in phase, produce 170 Hz waves. The speed of sound in air is 340 m/s. What is the phase difference (in radians) between the waves from A and B at the observer's location, point P?

A) 0
B) $\frac{\pi}{2}$
C) ( $\pi$ )
D) 2 $\pi$
E) 4 $\pi$