Three swings are installed in a playground, each with chains of equal length at $2\mathrm{.}5$ meters.

Each swing has a child with a different mass sitting on it: one child has a mass of $15$ kg$,$ another

$20$ kg$,$ and the third $30$ kg$.$ Assume that air resistance can be neglected and that the acceleration

of gravity is $9\mathrm{.}8$ m$/$s$^2.$ Which swing will oscillate with the highest frequency?