Missing index and prime

THanks to Manuel Hoff
https://stacks.math.columbia.edu/tag/00UK#comment-3966

algebra.tex

@@ -38590,10 +38590,10 @@ \section{\'Etale ring maps}
 }
 $$
 as in said lemma. Since the residue fields at $\mathfrak p$ and $\mathfrak p'$
-are the same, the fibre rings of $S/R$ and $(A \times B)/R'$
+are the same, the fibre rings of $S/R$ and $(A_1 \times B')/R'$
 are the same. Hence, by induction on the number of isolated closed points
 of the fibre we may assume that the lemma holds for
-$R' \to B$ and $\mathfrak p'$. Thus we get an \'etale ring
+$R' \to B'$ and $\mathfrak p'$. Thus we get an \'etale ring
 map $R' \to R''$, a prime $\mathfrak p'' \subset R''$ and
 a decomposition
 $$