(1a)Write a function named isLetter that accepts a character and returns true if the character is an alphabetic character, false otherwise. Your function should work for both upper and lower case characters. Use a RegExp to solve this problem.

(1b)Re-write your previous isLetter function as an arrow function.

(2a)Write a function named isVowel that accepts a character and returns true if the character a vowel, false otherwise. Your function should work for both upper and lower case vowels. Use a RegExp to solve this problem. AssumeY is a vowel.

(2b)Re-write your previous isVowel function as an arrow function.