Answer:
abstract class Mark  //Creating an Abstract class{
 abstract double getPercentage();}
class A extends Mark{
 double result;
 A( int val1, int val2, int val3){
  result=(val1+val2+val3)/3;}
 double getPercentage(){
  return result;}}
class B extends Mark{
 double result;
 B(int val1, int val2, int val3, int val4){
  result=(val1+val2+val3+val4)/4;}
 double getPercentage(){
  return result;}}
class Main{
 public static void main(String args[]){
  //class A Object
  Mark obj_1=new A(10,20,30);
  System.out.println(obj_1.getPercentage());
  //class B Object
  Mark obj_2=new B(10,20,38,46);
  System.out.println(obj_2.getPercentage());}}