teral
to a clause using a binary predicate $P$ and that previous literals
(including the head of the clause) contain five different variables.<br />

1.  How many functionally different literals can be generated? Two
    literals are functionally identical if they differ only in the names
    of the *new* variables that they contain.<br />

2.  Can you find a general formula for the number of different literals
    with a predicate of arity $r$ when there are $n$ variables
    previously used?<br />

3.  Wh