PART 1
The exponential decay model is given to be:
where a is the initial value and r is the decay rate.
In the question, the initial value is 15,500 and drops at a rate of 3%. This means that we have the following parameters:
Therefore, the exponential model is gotten to be:
PART 2
The graph of the function is shown below:
At x = 8000, we have the time as shown below:
The time will be 21.7 years.