| N = 0 | N = 5 | N = 10 | N = 30 | N = 45 | N = 60 | N = 90 |
Amazon | 4 | 6 | 10 | 14 | 15 | 16 | 17 |
iTunes | 3 | 5 | 9 | 14 | 14 | 15 | 16 |
Amazon or iTunes | 5 | 7 | 11 | 16 | 17 | 19 | 20 |
Amazon and iTunes | 2 | 4 | 8 | 12 | 12 | 12 | 13 |