Serendipity Booksellers has a book club that awards points to its customers based on the number of books purchased each month. The points are awarded as follows: 

• If a customer purchases 0 books, he or she earns 0 points.

• If a customer purchases 1 book, he or she earns 5 points.

• If a customer purchases 2 books, he or she earns 15 points.

• If a customer purchases 3 books, he or she earns 30 points.

• If a customer purchases 4 or more books, he or she earns 60 points. 

Write a program that asks the user to enter the number of books that he or she has purchased this month and then displays the number of points awarded.