Answer:
999
Step-by-step explanation:
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:
5 yrs+ 6 yrs =11 yrs
6 months+9 months=15 months
so,the answer is 11 yrs 15 months.