First generation: 3
Second generation:

Third generation:

Fourth generation:

And so on. The general formula for the

th generation is

. So by the 15th generation, you should expect around

geese.
The random variable is the number of cars held up at the intersection.
A random variable is one whose value is aleatory, then you can not know anticipatedly the outcome for sure. In this case, the number of cars held up at the intersection may be different at any time inside the range given and you cannot know the number of cars that there will be in a future moment.
This is the answer 14000 m