Two In-Phase Loudspeakers That Emit Sound with the Same Frequency

Multiple Choice

Two in-phase loudspeakers that emit sound with the same frequency are placed along a wall and are separated by a distance of 5.00 m. A person is standing 12.0 m away from the wall, equidistant
From the loudspeakers. When the person moves 1.00 m parallel to the wall, she experiences
Destructive interference for the first time. What is the frequency of the sound? The speed of sound
In air is 343 m/s.

A) 211 Hz
B) 422 Hz
C) 674 Hz
D) 256 Hz
E) 512 Hz