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Find the number of 5-digit telephone num...

Find the number of 5-digit telephone numbers having at least one of their digits repeated.

A

a) `^(n-3)C_(r-3) (r - 2)!`

B

b) `^n-3C_(r-2) (r - 3)! 3!`

C

c) `^n-3C_(r-3) (r - 2)!`

D

c) none of these

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