Desperately need physics help.?

I need to solve this question quickly: Two speakers are driven by a common oscillator at 860 Hz and face each other at a distance of 1.24 m. Locate the points along a line joining the two speakers where relative minima of the amplitude of the pressure would be expected. (Use v = 343 m/s. Choose one speaker as the origin and give your answers in order of increasing distance from this speaker. Enter 'none' in all unused answer boxes.)