Question: 2022 Winter Final - 1
Consider strings of length $70$, in which each character is one of the characters $a,b,c,d,e$. How many such strings have exactly $10$ letters $e$?
(a)
$\binom{70}{10}\cdot 5^{60}$
(b)
$\binom{70}{10}\cdot 4^{60}$
(c)
$\binom{70}{5}\cdot 4^{60}$
(d)
$5^{10}\cdot 4^{60}$
(e)
$\binom{70}{5}\cdot 5^{60}$