5. Another Mystery Recursion: public String mystery4 (String s, char ch) ( if (s.lengthO 2) ) else f return s; charffirst. chcharfirst.= s.charAt (1)) if (first-ch && first == s.charAt (1)) { { return mystery4 (s.substring (1), ch) ) else return s.charAt (0) mystery4 (s.substring(1), ch) Trace this mystery4 method for the following: mystery4("varriable","r")