Third program

interface calculate_result
{
 public void calculate_total();
 public void calculate_percentage();
 public void calculate_grade();
}

class student implements calculate_result
{
 int m1,m2,m3,tot=0;
 float per=0f;
 void get_marks(int ma1,int ma2,int ma3)
 {
  m1=ma1;
  m2=ma2;
  m3=ma3;
 }
 public void calculate_total()
 {
  tot=m1+m2+m3;
  System.out.println("Total marks: "+tot);
 }
 public void calculate_percentage()
 {
  per=tot/3;
  System.out.println("Percentage :"+per);
 }
 public void calculate_grade()
 {
  if(per>75)
   System.out.println("Grade A");
  else if(per<75 & per>55)
   System.out.println("Grade B");
  else if(per<55 & per>35)
   System.out.println("Grade C");
  else
   System.out.println("Fail");
 }

 public static void main(String args[])
 {
  student c= new student();
  c.get_marks(78,89,56);
  c.calculate_total();
  c.calculate_percentage();
  c.calculate_grade();
 }
}