Describe $in$ words the surface whose equation $is$ given.

$=\frac{}{6}$

the base $of$ the right circular cone with vertex $at$ the origin and axis the positive $z-$axis

the top half $of$ the right circular cone with vertex $at$ the origin and axis the positive $z-$axis

the plane perpendicular $to$ the $yz-$plane passing through $z=\frac{\sqrt[\phantom{2}]{3}}{3}y,$ where $y0$

the plane perpendicular $to$ the $xz-$plane passing through $z=\frac{\sqrt[\phantom{2}]{3}}{3}x,$ where $x0$

the plane perpendicular $to$ the $xy-$plane passing through $y=\frac{\sqrt[\phantom{2}]{3}}{3}x,$ where $x0$