Pressure problem(Fluid mechanic)

Rito3d03

1. The problem statement, all variables and given/known data

enclosed, thanks for checking

2. Relevant 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

Attached Thumbnails

 

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?