Subclasses and Inheritance

Hello,
this is a class Person that holds data such as name, id etc. on a person.
I need to develop a subclass of this called Student that inherits from Person,but also includes the data - credits(count of how many credits student has accumulated), and av_mark(average mark).
I also need accessor methods to return the data items credits and av_mark,but I think they are similar to the accessor methods in the Person class.Please help me out, I know nothing about inheritance or superclasses !

class Person
{
     
     protected Name name;
     protected char sex;
     protected String id;
     protected Person father;    
     protected Person mother;
     private static String tab = "";
     
     
     public Person (Name pname, char psex)
     {
          name = pname;
          sex = psex;
     }
     
     public Person (Name pname, char psex, String pid)
     {
          name = pname;
          sex = psex;
          id = pid;
     }
     
     public Name getname ()
     {  
          return name;
     }
     
     public char getsex ()
     {  
          return sex;
     }


     public String getid ()
     {  
          return id;
     }
     
     public void setid (String sid)
     {
          id=sid;
     }
     
     
     public void setMother (Person p)
     {
          mother = p;
     }

     public void setFather (Person p)
     {
          father = p;
     }

     public String toString ()
     {
          String s = new String (name + " (" + sex + ")");
       if (id !=null) s = s + " id: " + id;
       s += "\n";
       
       if(mother!= null)
              {    
                   tab += "  ";
                   s += tab + "mother: " + mother;
                   tab = tab.substring(2); // remove indent
              }
             
       if (father!= null)
                 {
                      tab += "  ";
                      s += tab + "father: " + father;
                      tab = tab.substring(2); // remove indent
                 }
          return s;    
     }
}