@MethodInformation(author="Wolfgang", date="09.12.2012", description="Gives back a double that describes the average of all used Gas of all fertilizing BioTraktor")
	protected double avgBioTraktorFertilizing() throws DivideByZeroException {
		MyIterator it = (MyIterator) traktoren.iterator();
		double sum = 0;
		int count = 0;
		
		while(it.hasNext()) {
			Traktor obj = (Traktor) it.next();
			
			if(obj instanceof BioTraktor) {
				if(obj.getMaschine() instanceof Duengstreuer) {
					sum += ((BioTraktor)obj).getAmount();
					count++;
				}
			}
		}
		
		if(count == 0)
			throw new DivideByZeroException();
		
		return sum/count;
	}