Complete the following program by developing the static method containsLetters(). The method looks for multiple letters in a given string and returns true if all the letters are present inside the string. Otherwise, it returns false. The search should be case insensitive. Hint: use the indexOf() method. public class Programl { public static void main(String args[]) { String s = "Hello world"; char[] search = {'l', 'o'}; boolean result = containsLetters (s, search); if (result) System.out.println("All letters are found."); else System.out.println("Not all the letters are found.")