Two vibrating tuning forks producing progressive waves given by;  $y_1=4\sin \left(500\pi t\right)$ ;  $y_2=2\sin \left(506\pi t\right)$  are held near the ear of a person. The person will hear;

3 beats/s with intensity ratio between maxima and minima equal to 2.

3 beats/s with intensity ratio between maxima and minima equal to 9. 

6 beats/s with intensity ratio between maxima and minima equal to 2.

6 beats/s with intensity ratio between maxima and minima equal to 9.