A mailman has thirty letters that each have a corresponding mailbox (all situated neatly together) in which each letter belongs. The mailman randomly places each letter in a mailbox. a) What are the odds that one letter was placed in the correct mailbox? b) What are the odds that AT LEAST one letter was placed in the correct mailbox? c) What are the odds that NO letters were placed in ANY of the correct mailboxes? d) How many possible permutations are there?