. What output is produced by the following code fragment in java ? Explain.

String s = abracadabra ;

int n1 = s.indexOf (ra ) ;

int n2 = s.indexOf (ra, 2 ) ;

int n3 = s.indexOf (ra, 5 ) ;

int n4 = s.indexOf (ra, 10 ) ;

System.out.println (n1) ;

System.out.println (n2) ;

System.out.println (n3) ;

System.out.println (n4) ;