The $x-t$ graph of a particle undergoing simple harmonic motion is shown below. The acceleration of the particle at $t=\raisebox{1ex}{$4$}\!\left/ \!\raisebox{-1ex}{$3$}\right. \mathrm{s}$  is,

In case of a simple harmonic motion, if the velocity is plotted along the $x$-axis and the displacement (from the equilibrium position) is plotted along the $y$-axis, the resultant curve happens to be an ellipse with ratio,

$\frac{\text{ major axis }\left(\text{along }x\right)}{\text{ minor axis }\left(\text{along }y\right)}=20\pi$.

What is the frequency of the simple harmonic motion?