A loudspeaker produces a steady sound wave in air. Its cone completes 200 oscillations in 0.50 s. At one instant, the centres of two neighbouring compressions are 0.35 m and 1.15 m from the loudspeaker. What is the speed of the sound wave?
80 m/s80\ \mathrm{m/s}80 m/s
500 m/s500\ \mathrm{m/s}500 m/s
320 m/s320\ \mathrm{m/s}320 m/s
160 m/s160\ \mathrm{m/s}160 m/s