non static method problem

non static method getpris cannot be referenced from a static context

her er klassen der giver fejlen

import java.util.*;
public class PurchaseStack extends java.util.Vector  {

private double total;
private int c;
 
  public PurchaseStack()    {

  c = 0;

}

public void push(Vare in)    {
  //true
  //post: in attached to container

  add(in);
}

public double purchaseSum()    {
  //true
  //post: return Sum of total[0..c[

  double b = 0;
  int i;
  Iterator it = iterator();
  while(it.hasNext())      {
  VareImpl tmp = (VareImpl)it.next();
  b = b + VareImpl.getPris();
 
  }
 
 
return b;
 
  }

}


den bruger denne klasse


/*
* forfatter: Ole Bloch
* forklaring: abstrakt klasse vare
* lavet: 17.02.2002
*
*
*/




public  class VareImpl implements VareSystemKrav    {
  protected double pris;
  protected double moms;
  protected String vareNr; 
  //konstruktør
 


  public VareImpl(double p)    {
  //pre: p > 0 && moms is a natural number
  //post: True
 
  this.pris = p;
 
  //set moms to 30 %
  this.moms = 30.0;
  this.moms = this.moms / 100;
 
  }//end constructor
 
  public  double getPris()      {

  return this.pris;


  }

}//end Vare

Hvad er der at gøre ved det