Suppose 9 balls are distributed amongst 12 urns in such a way that no more than one ball is put in any one urn, and that all such arrangements are equally likely.

(i) What is the probability that a specified urn will contain a ball?

(ii) If the urns are placed in a row before the balls are distributed, what is the probability that at least two of the first four urns will be empty?

Thanks for any help.