A $5\mathrm{.}0-$m radius playground merry$-$go$-$round with a moment of inertia of $2000kg*m^2$ is rotating freely with an angular speed of $1\mathrm{.}0ra\frac{d}{s}.$ Two people, each of mass $60$ kg $,$ are standing right outside the edge of the merry$-$go$-$round and suddenly step onto the edge with negligible speed relative to the ground. What is the angular speed of the merry$-$goround right after the two people have stepped on$?$

$0\mathrm{.}60ra\frac{d}{s}$

$0\mathrm{.}20ra\frac{d}{s}$

$0\mathrm{.}40ra\frac{d}{s}$

$0\mathrm{.}67ra\frac{d}{s}$