Physics about Density and pressure

Two liquids of densities 840kg/m3 and 1200kg/m3 are poured into the limbs of a U-tube until the difference in level of their upper surfaces is 0.9m. Calculate:
A, the heights of these surfaces above the interface. (2.1m,3m)
B, the pressure due to the liquid at the interface (25200N/m2)