A bookstore's sales are represented by a list of Sale objects populated with the name of the customer and the books they purchased.
public class Sale {
private String customer;
private List<Book> items;
// constructor, setters and getters not shown
}
public class Book {
private String name;
private double price;
// constructor, setters and getters not shown
}
Given a list of Sale objects, tList, which code fragment creates a list of total sales for each customer in ascending order?