at $t=0$
Particle is at $-\frac{A}{2}$ $\&$ moving towards negative extreme.
So. $(\mathrm{x}-3)=6 \sin (4 \pi \mathrm{t}+7 \pi / 6)$
$\mathrm{x}=3+6 \sin (4 \pi \mathrm{t}+7 \pi / 6)$

$(A)$ The force is zero $t=\frac{3 T}{4}$
$(B)$ The acceleration is maximum at $t=T$
$(C)$ The speed is maximum at $t =\frac{ T }{4}$
$(D)$ The $P.E.$ is equal to $K.E.$ of the oscillation at $t=\frac{T}{2}$

