Answer:
4 divided into 4000 is 1000 with no remainders
4/4000=1000
The exponential distribution is:

where

The probability we want is how likely will a dvd player last more than 8 years, given it has already lasted 5 years
To find this, you use conditional probability.

where A is P(x>8) and B is P(x>5)
To find these probabilities, integrate over the distribution:

Sub into conditional probability formula:

Final Answer: Given a dvd player is more than 5 years old, the probability that it will last another 3 more years is about 54.9%
Answer:
Option C - 1/81
Step-by-step explanation:
9^(-2) = 1/(9^2) [ Because a^(-m) = 1/(a^m) ]
so, 1/(9²) = 1/81.
Hope this helps you.