Consider the following mysterious method: public static int mystery(int a) ( if (a 0) return mystery(a); if (a 0) return 0; return a % 10 + mystery(a/10); Which is the best description of what this method does? Reason about it and then try running it in Eclipse. Try calling it with a few arguments such as mystery(10), mystery(15), mystery(24), mystery(-55). Returns the first decimal digit of its argument Returns the sum of the digits of the argument if it is positive or overflows the stack if negative Returns the sum of the digits of the argument Returns the first digit of its argument plus the rest of the number divided by 10