Mission 3 completed
	new file:   mission_3/attacks/hbb20/Book.rb
	new file:   mission_3/attacks/hbb20/Library.rb
	new file:   mission_3/attacks/hbb20/Member.rb
	new file:   mission_3/attacks/hbb20/book_explained.rb
	new file:   mission_3/attacks/hbb20/library_book_data.yml
	new file:   mission_3/attacks/hbb20/library_member_data.yml
	new file:   mission_3/attacks/hbb20/main.rb