There are 420 candidates sitting a public exam in a college. The sports hall can accommodate 210 students; once this has been filled there are other rooms available that are much smaller. The following is a list of the number of single desks that have been set up in each room: 26, 20, 24, 28, 24, 20, 24, 16, 20, 18, 26. The rooms have sufficient space for all the candidates who are not in the sports hall. The exams officer wants to leave the same number of empty desks in each of these rooms.