1.) Business Engineering or Manufacturing :)
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1) You don't know if the source is reliable.
2) It is better to cite reliable sources so.
The answer is true.
Let's say we are calculating the volume of a grain silo where the the width is a constant, but the height can be changed.
In our code we would calculate the volume using something like:
PI * (WIDTH / 2)^2 * height
The variables in all caps would be named constants. Using them makes the code more readable to other people than if we were to just use their values like:
3.14 * (145.75 / 2)^2 * height
