Given:
Number of people, n = 18
Let's determine the number of ways the top 5 finishers can be arranged.
Here, we are to use the permutation formula.
Apply the formula:

Where:
n = 18
r = 5
Thus, we have:

Solving further:

Therefore, there are 1,028,160 ways in which the top 5 finishers can be arranged.
ANSWER:
1) 1,028,160