<span>B. Square the number of the term, n</span>
11: 4,874 > 4,784 > 4,687
12: 8.09 > 8.057 > 8.023
13: 15.820 > 15.280 > 15.000
14: 43,628 > 40,628 > 34,628
15: 395.050 > 395.009 > 395.005
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: