A mass on a spring vibrates horizontally on a smooth level surface (see the figure). Its equation of motion is $x(t)=3 \sin{t}$, where $t$ is in seconds and $x$ in centimeters.
(a) Find the velocity at time $t$.
(b) After finding the velocity of the mass at time $t=2\pi/3$, in what direction is it moving at that time?
Answer "l" for left or "r" for right below.

$v(t) =$
direction: