Use the fileUN.txt that gives data about the 193 members of the United Nations with the countries listed in alphabetical order. Each line of the file gives the name, continent, population (in millions), and area (in square miles) of aU.N.member. Some lines of the file are

Write a program that uses the fileUN.txt to determine the names of the continents that contain countries, and places the continents in alphabetical order in a list box. See Fig.8.18. Hint: Use set comprehension.