NA$11$

$()()$ R $[$X$]/$S $=\{([$x$]/$S$,[$y$]/$S$)|($x$,$ y$))$ E R$\}13($X$,$ S$)($Y$,<)($x$,$ y$)=($x$\text{'},$ y$\text{'})$ iff $($x Sx$\text{'})^($y y$\text{'})($X x Y$,$ S$)14$ X $$ C$\text{'}$ C C$\text{'}$ iff SEC$=($ES$\text{'}$ E C$\text{'})$ S CS$\text{'}$YDon$\text{'}$t Solve $$