$(6)(Bonus)If$ a particle moving along a curved track $(like$ a roller coaster$)$ flies off the track, $it$ continues $in$ the direction $of$ the tangent vector $at$ the point where $it$ left the track, $at$ least $if$ there are $no$ external forces such $as$ gravity $or$ friction acting $onit.$ Suppose a particle rolling down $(towards$ the $xy-$plane$)$ the helix shaped track given $by$ vec$(r)(t)=($:$2cost,2sint,-t$:$)$ flies off the track when $t=\frac{}{4}.$ Determine the point where the particle will hit the $xy-$plane.