The 25 member states of the European Union set up a committee with the following rules:
1) the committee should meet daily;
2) at each meeting, at least one member should be represented;
3) at any two different meetings, a different set of member states should be represented;
4) at nth meeting, for every k<n, the set of states represented should include at least one state that was represented at the kth meeting.For how many days can the committee have its meetings? combinatorics unsolvedcombinatorics