Two Loudspeakers S₁ and S₂, 3

Multiple Choice

Two loudspeakers S₁ and S₂, 3.0 m apart, emit the same single-frequency tone in phase at the speakers. A listener directly in front of speaker S₁ notices that the intensity is a minimum when she is 4.0 m from that speaker (see figure) . The listener now walks around speaker S₁ in an arc of a circle, staying 4.0 m from that speaker but increasing her distance from the other speaker. How far is she from speaker S₂ when she notices the first maximum in the sound intensity? The speed of sound in air is 340 m/s.

A) 4.5 m
B) 5.0 m
C) 5.5 m
D) 6.0 m
E) 6.5 m