Calculating the work against gravity?

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To calculate the work against gravity for building a brick tower with a height of 20 feet and a base of 10 feet, the volume of each layer is determined to be 100Δy ft³. The mass of each layer is calculated using the brick's density of 80 lb/ft³, resulting in a force of 78,400 lb acting on each layer. The integral of this force over the height of the tower is computed, but there is a discrepancy with the expected answer in the solutions manual, which states the work should be 1.6x10^6 ft-lb. The correct acceleration due to gravity is clarified as 32 ft/s², which is essential for accurate calculations. This discussion highlights the importance of using the correct gravitational constant in work calculations against gravity.
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Calculate the work against gravity require to build the structure out of brick. Assume the brick has a density of 80 lb/ft^3.

A tower has a height of 20ft and a square base of side 10ft.

This is what I tired to do. I may have gotten it right, but the units or something may have been off. I am hoping one of you will be able to help me.

Volume of layer = 10 x 10 Δy ft^3 = 100Δy ft^3
Mass of layer = 80 lb/ft^3 x 100Δy ft^3
Force on layer = 9.8 x 80 x 100Δy = 78400

Taking the integral of 78400y from limits 0 to 20 equals 15,680,000, but the answer in my solutions manual says the answer should be 1.6x10^6 ft-lb.

Can anyone help me out?
 
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What is the acceleration of gravity in ft/s2?
 
I'm not sure. Those were the only givens.
 
I guess you are supposed to know that g = 32 ft/s2. Use that.
 

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