Calculating Force on a Tank Hatch in Water

[VelvetRebel]

Force of a Tank Hatch in terms of Pressure

Homework Statement

The tank shown in the figure below is filled with water to a depth of H1 = 1.88 m.
http://educog.com/res/brookscole/serway/Physics_for_Scientists_and_Engineers_6ed/Chap14/graphics/serb1514.gif
At the bottom of one of the side walls is a rectangular hatch H2 = 1.15 m high and W = 1.90 m wide. The hatch is hinged at its top. Determine the magnitude of the force that the water exerts on the hatch.

Homework Equations

F=\int^{H1-H2}_{0} W\rho g(H1-y)dy

The Attempt at a Solution

The equation above is what my professor gave us in class to use for this problem.
For the solved integral, I got:
W\rhog[H₁y-y²/2]
After putting in all the numbers, I don't get the right answer. Is my solved integral wrong? Or did my professor give us the wrong integral?

 

[mgb_phys]

Before you do the maths, think about the answer.
Specifically think about what a integral means in this case.

(hint - 'average' pressure on the hatch?)

 

[VelvetRebel]

EDIT: Nevermind, I figured it out.