User IDs on an old computer system consist of 4 letter sequences from the first 8 letters of the English alphabet: a, b, c, d, e, f, g, h. Note that the same letter can be used any number of times in the 4 letter sequence. When a new user first registers, an ID is randomly generated (all outcomes equally likely) with the only condition that it is different from the IDs of all previously registered users. (a) How many different IDs are possible for the first registered user? (b) How many different IDs are possible for the second registered user? (c) Jack, Kate and Sam are the only three users of this system. In how many different possible ways can they be assigned IDs?