| In a certain country, 10-digit telephone numbers with the following format were introduced: |
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| Digits may be repeated. |
| 10.1 | How many possible 10-digit telephone numbers could be formed? | (2) |
| 10.2 | Certain restrictions were placed on the groups of digits: - Area code: must be 3 digits and the first digit can NOT be 0 or 1
- Exchange code: must be 3 digits and the first and second digits can NOT be 0 or 1
- Number: must be 4 digits and the first digit MUST be a 0 or 1
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| 10.2.1 | How many valid 10-digit telephone numbers could be formed by applying the given restrictions? | (3) |
| 10.2.2 | Determine the probability that any randomly chosen 10-digit telephone number would be a valid phone number. | (2) |
| | [7] |