If the following methods are declared in a class, which of them fail to compile because of overloading rules?

public static int f$2($int a$,$ int b$)//1$

public static double f$2($double a$,$ int b$)//2$

public static double f$2($int a$,$ double b$)//3$

public static void f$2($double a$)//4$

public static int f$2($double b$)//5$

public static void f$2($int a$)//6$

Your answer:

$2,3,4,5$ and $6$

$4,5$ and $6$

$4$ and $5$

$5$ and $6$