To solve this, we first determine the number of ways to select 4 countries from 15, we calculate number of ways to visit these 4 places then we multiply.
Selecting number of ways to choose 4 cities from 15 is by using the combination formula, which becomes 15C4
Number of ways to visit these 4 cities = 4!
Hence,total number of ways of visiting these 4 cities = 15C4 * 4! = 32760ways
