Answer:
3,265,920 unique ID exist.
Explanation:
The nine digits are from 0 to 9, there are ten bits from 0 -9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
The first is select from the highest bit (9), and the second is selected at random from 0 - 9, the third bit to the last must be unique and different from each other;
number of unique IDs = 9 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2
Multiplying the nine bits of unique IDs = 3,265,920.
