What is the pressure at points A, B, C & D marked in the given mercury barometer? Assume that you have used a tube of length greater than 76cm and then filled it completely with mercury and then inverted into a jar. Let P0 be atmospheric pressure, g be acceleration due to gravity and ρ be the density of mercury.

Fluid pressure is the force per unit area that acts on an object in the fluid or on a closed container's surface.

The cause of this pressure is due to acceleration, gravity, or by forces that are outside the closed container.