A large rock weighing 164N is suspended from a 3 meter wire. The density of the rock is rho_rock = 3200 kg/m^3, and the wire mass is negligible. The upper end of the wire is fixed; in air the frequency is 40Hz while in liquid the frequency would be 25Hz. Find the density of the liquid.
The rock has mass 16.7kg, and I know that v = lambda*f but I don't know what to do from here