1 .
You roll a fair die 18 times; the rolls are independent of each other. What is the probability that
you roll a 5 exactly three times?
(a)
${18 \choose 3} \cdot \left. 5^{15} \middle/ 6^{18} \right.$
(b)
None of the above.
(c)
${18 \choose 3} \cdot \left(5 \middle/ 6 \right)^{18}$
(d)
$18 \cdot \left. 5^{15} \middle/ 6^{18} \right.$