Exercise #12: "Boolean Zen" This attempted solution to Self-Check 5.15 (isvowe1) has several problems: // Returns whether the given string represents a vowel: // a, e, i, o, or u, case insensitively. public static boolean isVowel (String s) if (s -- "a") { return true; ) else if (s "e") return true ) else if (s "i") return true else if (s"o" return true; else if (s"u") return true; else f return false