Math 2602  B1 , B2                                                                          Homework  #4
                                           Due Tuesday, February 8, 2005

1. How many of the words of length 12, which can be formed using the alphabet { A , C , G , T }, have

    i)  exactly four C's ?

   ii)  at least one C and at least one T ?

  iii)  exactly one A and at least one C ?