Fluid pressure in a tank - manometer

[Happy4ever]

Homework Statement

The level of benzene in a storage tank may fluctuate between 10 cm and 300 cm from the top of the tank. Since it is impossible to see inside the tank, an open-end manometer fluid is to be used to determine the benzene level.
One leg of manometer is attached to the tank at the position of 400 cm from the top. A nitrogen blanket at atmospheric pressure is maintained over the tank contents. (as in image)

What manometer readings R(cm) would be observed at the extremes of the benzene level with water/ mercury as the manometer fluid?
which manometer fluid would you use and why?

Homework Equations

P=ro*g*h + P(atm)

The Attempt at a Solution

the P at both legs of the manometer where the fluid is same level is same so
P(on open end of manometer) = P(atm) + ro (density of water as manometer fluid)*g*R

same for Pressure in the tank (at other end of manometer whith P of benzene in tank) =
P(atm) + ro(Benzene) *g* H (which is height of column of Benzene in tank )

and these two pressures are the same ,
by having H then we can find R . The problem is that I can't figure out how to find H, because we have the manometer 400 cm from top , but it doesn't say about the height of column of benzene on the manometer leg.

Thanks

 

[Angie Aaron]

i need help on this question

 

[TeethWhitener]

i need help on this question

Welcome to PF!

Make sure to read the Terms and Rules. We don't typically answer homework questions straight away. We would ask you to show what work you've done on the problem and then try to guide your thinking in the right direction. Also of note, the "Open practice problem" section is a little weird in that it consists of years-old unanswered threads that serve as practice problems for whomever. I can try to ask the mentors to migrate this problem back to the homework section, but you'll probably need to show what work you've done so far on the problem.

 

[berkeman]

i need help on this question

Welcome to the PF.

Please re-post in the Homework Help, Introductory Physics Homework forum (not the Open Practice Problems forum), and fill out the Homework Help Template you are provided there. This includes sections on the Relevant Equations and your Attempt at a Solution.