Question

5. I stand in the exact center of the concert hall. Two speakers very close to each other on stage are broadcasting A4 (F440 Hz)·l then start walking to the right, parallel to the stage. hear the sound phase out then come back. How far did I walk laterally to the stage? (Note vsound-343 m/s) A) 0.39 m B) 0.78 m C)0.99 mD 1.28 m