fixing typo

book.tex

@@ -4363,9 +4363,9 @@ Figure~\ref{fig:tuple-rep} to see how the tag is organized. We
 recommend using the Racket operations \code{bitwise-ior} and
 \code{arithmetic-shift} to compute the tag.  The \itm{types} in the
 type annotation in the \code{allocate} form can be used to determine
-the pointer mask region of the tag. The move of \itm{lhs}^\prime to
+the pointer mask region of the tag. The move of $ \itm{lhs}^\prime $ to
 register \code{r11}, before the move to the offset of \code{r11}
-ensures that if \itm{lhs}^\prime offsets are only performed with
+ensures that if $ \itm{lhs}^\prime $ offsets are only performed with
 register operands.
 \begin{lstlisting}
    (assign |$\itm{lhs}$| (allocate |$\itm{len}$| (Vector |$\itm{types}$|)))