Question 13
The addition below is incorrect. The display can be made correct by changing one digit $d,$ wherever it occurs, to another digit $e.$ Find the sum of $d$ and $e.$
$$
\begin{array}{rrrrrrr}&7&4&2&5&8&6\\+&8&2&9&4&3&0\\\hline1&2&1&2&0&1&6\end{array}
$$
$$
\begin{array}{rrrrrrr}&7&4&2&5&8&6\\+&8&2&9&4&3&0\\\hline1&2&1&2&0&1&6\end{array}
$$