ANSWER: 15
N(N-1)/2 for N=6 gives 6(6-1)/2 = 6(5)/2 = 30/2 = 15
OR
| May | Nash | Overton | Pickens | Queen | Rogers | |
| May | ---------- | 1 | 2 | 3 | 4 | 5 |
| Nash | ---------- | ---------- | 6 | 7 | 8 | 9 |
| Overton | ---------- | ---------- | ---------- | 10 | 11 | 12 |
| Pickens | ---------- | ---------- | ---------- | ---------- | 13 | 14 |
| Queen | ---------- | ---------- | ---------- | ---------- | ---------- | 15 |
| Rogers | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- |