Pressure problem(Fluid mechanic)

[Rito3d03]

1. Homework Statement

enclosed, thanks for checking

2. Homework Equations

P = ρgh

3. The Attempt at a Solution

I have try to add up all pressure in the tank
(including gauge pressure, pressure of the oil(ρg*0.5), pressure of the water(ρg*0.8))
but still can't balance out the equation since the answer of part A is 1.4m

also, I don't have any clue about part B

thanks if anyone can give me any help

 

[haruspex]

Let's see you working. In terms of depth of water, how much pressure at the bottom of the tank comes from:
- The gas above the oil
- The oil
- The water in the tank?

For B:
- what is the pressure at the water/Hg boundary?
- what height of Hg is that equivalent to?