Answer:
The answer is option (C), One cement bridge post weighs 9,135 pounds
Step-by-step explanation:
Step 1: Get the total volume of a cement bridge post
The cement bridge post is in the shape of a cuboid, therefor the volume of the cement bridge post can be expressed as;
Volume of cement bridge post=Base area×Length
where;
Base area=(24^2) inches square
1 foot=12 inches
Convert 24 inches to foot=24/12=2^2=4 feet²
Length=15 feet and 9 inches
1 foot=12 inches
Convert 9 inches to foot=9/12=0.75 feet
Total length=(15+0.75)=15.75 feet
replacing;
Volume of cement bridge post=(4×15.75)=63 cubic feet
Volume of cement bridge post=63 cubic feet
Step 2: Get the total weight of the cement bridge post
Total weight of the cement bridge post=Weight per cubic foot×total volume of the cement bridge post
where;
Weight per cubic foot=145 pounds per cubic foot
Total volume of the cement bridge post=63 cubic feet
replacing;
Total weight of the cement bridge post=(145×63)=9,135 pounds
One cement bridge post weighs 9,135 pounds
Then for substitution:dx=u du. and integral becomes:
=u-ln(u+1)=
. Now we will change the values of limits: 
=4-ln(5)-2+ln(3)=2+ln(0,6)=2-0.51=1.49