Answer:
If I'm correct I think 4 is the polygon
I'm sorry idk how to do it
For this case we have the following equation:

Where,
w: The weight of a spring in pounds
E: the energy stored by the spring in joules.
Substituting values we have:

Making the corresponding calculation:
Answer:
the approximate weight of the spring in pounds is:
Answer:
I do 1 option for you as an example, you need to check the leftover by yourself.
Step-by-step explanation:
for d) y(0) = 0 and y'(pi) =0



Replace
we have
if and only if 
Hence the given solution does not work.
then, d is NOT the correct answer.