Let $ONE$-$OR$-$ALL$($L$\_1,$ L$\_2,$ L$\_3)$$ be the set which contains all strings which are either members of all three languages $L$\_1,$ L$\_2,$ L$\_3$$ or are contained in $\backslash$emph$\{$exactly$\}$ one of the three languages. Show that, if $L$\_1,$ L$\_2$$$,$ and $L$\_3$$ are regular, then $ONE$-$OR$-$ALL$($L$\_1,$ L$\_2,$ L$\_3)$$ is also regular.