text: #ifndef _BOOK_H_
  #define _BOOK_H_
  #include <string>
  
  class Book {
    std::string title, author;
    int length;
   protected:
    int getLength() const;
   public:
    Book(const std::string &title, const std::string &author, int length);
    Book(const Book &b);
  
    std::string getTitle() const;
    std::string getAuthor() const;
    virtual bool isHeavy() const;
  
    virtual bool favourite() const;
  };
  
  #endif
  