Work compute with integral

A tank is full of water. Find the work *W* required to pump the water out of the spout. Use the fact that water weighs 62.5 lb/ft3.

*a* = 5 *b* = 9 *c* = 12

http://www.webassign.net/scalcet/6-4-024alt.gif

So for this one, you have to set up an amount of rectangles.

The biggest rectangle is 5(or y) by 9, in relation to a smaller rectangle that is w by 9. I can also setup a relationship between the two to find that y/w=9/9 or y=w. So therefore we can produce an equation for the area of one rectangle.

dA=9y

Now the thickness of this rectangle is extremely small so the thickness is dy.

dV=9y dy

The density of water is 62.5 lb/ft^3, so this one rectangular-box of water is:

dM=562.5y dy

To find the force, we multiply by the force of gravity, I used 32.2 ft/sec^2.

dF=18112.5y dy

So our work is dF times the distance. This is where I become lost. Would the distance be vertical or horizontal? would it be (5-y) or (12-y)?