 Solution

ID: past-exam-of-the-year-1-of-the-computer-science-course-of-the-university-of-oxford/2022/discrete-mathematics-continuous-mathematics-and-probability/discrete-mathematics/1/a/i/solution

∣ ⋃_{i = 1}^{n} A_{i} ∣ = \sum_{i = 1}^{n} ∣ A_{i} ∣.

The password sets of different lengths are disjoint, so the required number is $P_{4} + P_{6} + P_{8}$ .

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