The arm of the robot moves so that $r=3 \mathrm{ft}$ is constant, and its grip $A$ moves along the path $z=(3 \sin 4 \theta) \mathrm{ft}$ where $\theta$ is in radians. If $\theta=(0.5 t)$ rad, where $t$ is in seconds, determine the magnitudes of the grip's velocity and acceleration when $t=3 \mathrm{s}$