
Answer:
 1.504Ă10âś ft¡lb
Step-by-step explanation:
We understand the top of the oil in the tank is 12 ft below ground level, and the bottom of the tank is 8+18=26 ft below ground level. Then the average depth of the oil is (12+26)/2 = 19 ft below ground level.
The height of the oil in the tank is 26-12=14 ft, so the volume of it is ...
 V = Ďr²h = Ď(6 ft)²(14 ft) = 504Ď ftÂł â 1583.36 ftÂł
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So, the work required to raise that volume of oil to the surface is ...
 (1538.36 ftÂł)(50 lb/ftÂł)(19 ft) = 1.504Ă10âś ft¡lb