Two spheres P and Q of equal radii have densities $\rho_1$ and $\rho_2$, respectively. The spheres are connected by a massless string and placed in liquids $L_1$ and $L_2$ of densities $\sigma_1$ and $\sigma_2$ and viscosities $\eta_1$ and $\eta_2$, respectively. They float in equilibrium with the sphere P in $\mathrm{L}_1$ and sphere Q in $\mathrm{L}_2$ and the string being taut (see figure). If sphere $P$ alone in $L_2$, has terminal velocity $\vec{V}_P$ and $Q$ alone in $L_1$ has terminal velocity $\vec{V}_Q$, then