@MethodInformation(author="Matthias", date="09.12.2012", description="Gives back a double that describes the average carrying capacity of all BioTraktor")
	protected double avgCapacityBio() throws DivideByZeroException{
		MyIterator it = (MyIterator) traktoren.iterator();
		double sum = 0;
		int count = 0;
		
		while(it.hasNext()){
			Traktor tractor = (Traktor) it.next(); //I don't know which way is the better :/
			
			if(tractor instanceof BioTraktor){
				if(tractor.getMaschine() instanceof Duengstreuer){
					sum += tractor.getMaschine().getDetailOfMaschine();
					count++;
				}
			}	
		}
		
		if(count == 0)
			throw new DivideByZeroException();
		
		return sum/count; 
	}