A rectangular vessel of dimension (l × b × h) and mass M contains a liquid of density ρ. The vessel has a orifice at its bottom at a distance c from the rear wall as shown in fig.

The maximum amount of water that can be retained is shown in the fig. If θ is the angle made by the water surface with the horizontal then.tan⁡θ=hc=ag ⇒a=hgcSo the maximum volume that can be retained is 12×h×c×bAnd F=M+hcbρ2hgc