In the (fictional) dice game Piracy, a player begins a turn by rolling a handful of 13 (fair, independent, six-sided, standard) dice.
a) The order of the dice doesn't matter for gameplay. All that matters is how many of each number is rolled. How many different rolls are possible?
b) What is the probability of rolling 2 ones, 1 two, 4 threes, 3 fours, 2 fives, and 1 six?
c) What is the probability that there will be at least three dice showing the same number?