A mass suspended from a spring is pulled down a distance of $2$ ft from its rest position, as shown in the figure. The mass is released at time $t=0$ and allowed to oscillate. If the mass returns to this position after $2$ s $,$ find an equation that describes its motion.

$y=-2cost$

$y=-2sint$

$y=-2cost$

$y=-2sint$

$y=-4sint$