It could be 400 sets of 4 digits.
<h3>What is permutation and combination ?</h3>
combination and permutation are two different ways of grouping elements of a set into subsets. In a combination, the elements of the subset can be listed in any order The components of the subset are listed in a permutation in a certain order.
Given that: Alan is aware that the first digit is nine and the final digit is greater than five.
Optional first digit: 1 (9)
10 choices for the second digit (0 to 9)
10 choices for the third digit (9 to 9)
Optional fourth digits: 4. (6, 7, 8, 9)
Possibility of sets:
1×10×10×4 = 400
To know more about permutations and combinations visit:
brainly.com/question/20385533
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