In our flying system we want to develop a simple game to our passengers. The game works as follows. The program is taking text from the passenger, once the passenger enters text, two other components (Listeners) of the program are informed that the text has been changed. The first Listener will display the text in reverse and the other will display the information about the text that include (number of characters, number of vowels and number of words). What is the suitable design pattern to use and why?

(please just answer the question in bold letters)