fixes

book.tex

@@ -6390,7 +6390,7 @@ in Figure~\ref{fig:Lif-syntax}. The \LangIf{} language includes all of
 operators to include
 \begin{enumerate}
 \item subtraction on integers,
-\item the logical operators \key{and}, \key{or} and \key{not},
+\item the logical operators \key{and}, \key{or}, and \key{not},
 \item the \racket{\key{eq?} operation}\python{\key{==} and \key{!=} operations}
   for comparing integers or Booleans for equality, and
 \item the \key{<}, \key{<=}, \key{>}, and \key{>=} operations for