- A$3\, beats/s$ with intensity ratio between maxima and minima equal to $4$
- ✓$3 \,beats/s$ with intensity ratio between maxima and minima equal to $9.$
- C$6\, beats/s$ with intensity ratio between maxima and minima equal to $4.$
- D$6\, beats/s$ with intensity ratio between maxima and minima equal to $9.$

