A playground merry$-$go$-$round has a mass of $120$ kg and a radius of $1\mathrm{.}80$ m and it is rotating with an angular velocity of $0\mathrm{.}600$ rev$/$s$.$ What is its angular velocity $($in rev$/$s$)$ after a $25\mathrm{.}0$ kg child gets onto it by grabbing its outer edge? The child is initially at rest.