"A vertical cross section of a tank is shown ( in attachment ). Assume that the tank is 16 feet long and full of water. ( delta = 62.4 pounds per cubic foot ) and that the water is to be pumped to a height 8 feet above the top of the tank. Find the work done in emptying the tank."

So, work = force * distance. The force should be the weight of the tank, found by the volume ( l * w * h ) times delta. The distance should be ( 16 - y ).

I'm at a complete loss here. Starting with the algebra involving that diagram to find volume. The 'help me solve this' doesn't elaborate on what it's doing.

Next, I know the limits of integration are 0 to 8, but I do not understand why they are.