public static Promotion addPromotion(Promotion p) {
		if (p == null)
			return null;

		// We check if the promotion doesn't still exist in the Professor List.
		boolean exist = false;
		int pos = 0;
		for (int i = 0; i < FileReadService.pList.size(); i++) {
			if (FileReadService.pList.get(i).equals(p)) {
				exist = true;
				pos = i;
			}
		}

		if (!exist) {
			FileReadService.pList.add(p);
			return p;
		}
		return FileReadService.pList.get(pos);
	}