A cube of density $\rho_{c}$ floats in a liquid of density $\rho_{1}$ as shown in the figure, At rest, an amount $h$ of the cube's height is submerged in liquid. If the cube is pushed down, it bobs up and down like a spring and oscillates about its equilibrium position. Show that the frequency of its oscillations is given by $f=(2 \pi)^{-1} \sqrt{g / h}$.