a$)$ Create a method named "replaceVowels$\_3"$ that takes a String input and returns a new String with all vowels replaced by $\text{'}$@$\text{'}.$ b$)$ Implement another method named "UpperString" that display all the letters of a given String in upper case. c$)$ Implement a third method named "StartWith$\_$J$"$ that takes a String input and returns true or false message if the string starts with the letter $"$J$"$ or not.