A Hydrometer? PHYSICS HELP QUESTION?

A hydrometer is a simple instrument used to indicate specific gravity of a liquid by measuring how deeply it sinks in the liquid. A particular hydrometer (Fig. 10-15) consists of a gl tube, weighted at the bottom, which is 25.0 cm long, 2.00 cm2 in cross-sectional area, and has a m of 42.5 g. The hydrometer sinks to a depth of 24.6 cm when placed in a fermenting vat. What is the density of the brewing liquid?