Ambiguity In Overloaded Functions

I have an overloaded function 'f' as follows:

1. public void f(int i, long j){System.out.println("1");}
2. public void f(int...i){System.out.println("2");}
3. public void f(long l, long p){System.out.println("3");}
4. public void f(int j, int k){System.out.println("4");}

With the function call: f(1,2), the output is: 4.

My questions are the following:

a. Why is the compiler choosing #4 to execute and not the rest?
b. If I remove 4 and replace it with: 5. public void f(long j, int k){System.out.println("5");}, why does the compiler now give an error complaining of ambiguous function defintions when 'f' is called?