Need help with fluids and pressure problem

[SOLVED] need help with fluids and pressure problem

1. Homework Statement
The L-shaped tank shown below is filled with water and is open at the top.
(a) If d = 4.0 m, what is the force on face A due to the water?
N (up)

(b) What is the force on face B due to the water?
N (right)

2. Homework Equations
F=PA

3. The Attempt at a Solution
Fa=PaAa+Patmosphere
Pa=pgHa
Ha=2d
Fa=pg2d^3+Patmosphere
d=4
I got 2.85x10^6N but that was wrong
I was given this hint when i got it wrong:Can you find the pressure at a given depth? How is force related to pressure for a given horizontal surface area? On the vertical wall, how does pressure vary with depth along the wall? Do you see that you need to first consider a strip that has the wall's width but only a differential height dy? What is the force on the strip? Do you see that you next must integrate to find the force on the full wall (all the horizontal strips)?
is this how it should be done:
Fa=Integral(pgd^2 dy)+Patmosphere

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