Someone

	public function get transfer_rate():Number
	{
		var head:Object = progressions.getHead();
		var tail:Object = progressions.getTail();
		
		if (head != null && tail != null)
		{
			var elapsed_time:Number = head.time - tail.time;
			var bytes:Number = head.bytes - tail.bytes;
			
			return( bytes / elapsed_time );
		} else
			return( 0 );
	}