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 .

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