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1 . Consider strings of length $78$, in which each character is one of the characters $a,b,c,d,e$. How many such strings have exactly $17$ letters $e$?
(a)
$\binom{78}{5}\cdot 5^{61}$
(b)
$\binom{78}{5}\cdot 4^{61}$
(c)
$5^{17}\cdot 4^{61}$
(d)
$\binom{78}{17}\cdot 5^{61}$
(e)
$\binom{78}{17}\cdot 4^{61}$
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