A $5\mathrm{.}0-$m radius playground merry$-$go$-$round with a moment of inertia of $2000$ kg$$m$2$ is rotating freely with an angular speed of $1\mathrm{.}0$ rad$/$s$.$ Two people, each having a mass of $60$ kg are standing right outside the edge of the merry$-$go$-$round and step on it with negligible speed. What is the angular speed of the merry$-$go$-$round right after the two people have stepped on$?$

Group of answer choices

$0\mathrm{.}60$ rad$/$s

$0\mathrm{.}67$ rad$/$s

$0\mathrm{.}20$ rad$/$s

$0\mathrm{.}80$ rad$/$s

$0\mathrm{.}40$ rad$/$s