Two identical loudspeakers 2.50m apart are emitting sound

Last updated: 7/31/2022

Two identical loudspeakers 2.50m apart are emitting sound waves into a room where the speed of sound is 340m/s. Abby is standing 4.50 m in front of one of the speakers, perpendicular to the line joining the speakers, and hears a maximum in the intensity of the sound. What is the lowest possible frequency of sound for which this is possible? Don't forget to include units for your answer!