the answer should be 0.14 m. please explain how to solve this

Two tanks are separated by a massless, Lshaped gate as shown. The left side of the gate contains water of density w=1000 kg/m3 while the right side of the gate contains oil of density 0=600kg/m3. The tops of both sides of the tank are open to air at atmospheric pressure, Patm. The known lengths are a=1m,b=1m, and c=0.25 m. The oil surface is at height h above the hinge, as shown. The gate can swing freely to the right if not forced closed by the weight of the oil. Determine the minimum height, h