A sound wave produced by a loudspeaker is sent back by a reflector along the same path. At first, the microphone is at point $X$, where the sound intensity is at a minimum, as shown. The microphone is then moved towards the reflector and goes through four further intensity minima before arriving at a fifth minimum at point $Y$. The distance $XY$ is $70.0\,\text{cm}$. Determine the wavelength of the sound.
- A$11.7\,\text{cm}$
- B$14.0\,\text{cm}$
- C$23.3\,\text{cm}$
- D$28.0\,\text{cm}$