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Question: 2017 Winter Final - 10

Author: Michiel Smid
We choose, uniformly at random, a string consisting of 14 characters, where each character is a lowercase letter. Let $A$ be the event
  • A = "the string contains at least one vowel".
(A vowel is one of the letters $a$, $e$, $i$, $o$, and $u$.) What is $\Pr(A)$?
(a)
$1 - (26/21)^{14}$
(b)
$1 - (21/26)^{14}$
(c)
$14 \cdot (5/26) \cdot (21/26)^{13}$
(d)
$5 \cdot (5/26) \cdot (21/26)^{13}$