It's a coffin because the person who makes it is alive so they don't need to use it, the person who buys it is also alive and buying it for someone else.
The person who is using it has passed away so they can't see or feel anything.
:( This is one morbid riddle.
Answer:
10
or 14.14 appromiximately
Step-by-step explanation:
Area of square = 100
So length on side = 10 because all sides of square equal.
Length of Diagonal = Side x 
So the length of diagonal is 14.14 approximately
Answer:
Step-by-step explanation:-12x=2
X=-12/2
X=-6