Please explain

The figure below shows a well that is 12,000 ft deep. The bottom H = 2,000-ft portion is filled with an incompressible oil (SG = 0.75), above which there is an h = 10,000-ft layer of methane (CH4; C= 12, H = 1) at 100 F, which behaves as an ideal isothermal gas whose density is not constant. The gas and oil are static. The density of water is 62.3 lbm/ft. a) If the pressure gauge at the top of the well registers pA= 1,000 psig, compute the absolute pressure p (psia) at the oil/methane interface. Work in terms of symbols before substituting numbers. b) Also compute (pc-ps), the additional pressure (psi) in going from the interface B to the bottom of the well C. A Methane B Oil C H