These three classes are in separate Java files the same directory.What is the output if Dog is run? public class Dog extends Mammal {public static void main (string [] args) {new Dog ();}//end main public Dog () {system. out. println ("dog");}//end constructor}//end class Dog public class Mammal extends Animal {public Mammal () {System. out. println ("mammal");}//end constructor}//end class Mammal public class Animal {public Animal () {this ("animal 2"); system. out. println ("animal 1");}//end constructor Animal public Animal (String s) {System. out. println (s);}//end constructor Animal}//end class Animal