Event 4 (impossible), Event 3 (probability is 7/20), Event 1 (probability is 6/12 which is greater than 7/20), and Event 2 (certain to happen)
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:
C a1= -2
an = an-1 +3
Step-by-step explanation:
an = -2+ (n-1)3
What is the first term? Let n=1
a1 = -2 + 0*3
a1 = -2
The difference between the terms is +3 (coefficient on (n-1))
The second term is the first term +3
The third term is the second term plus 3
The next term is the previous term +3
so an = an-1+ 3