;@problem$7$

$($define $($three$-$criteria$-$courses c$)$

$($cond

$[($empty$?$ c$)$ empty$]$

$[$else

$($local

$[($define $($fn$-$for$-$course c$)$ ;

$($cons $($course$-$number c$)($fn$-$for$-$loc $($course$-$dependents c$))))$

$($define $($fn$-$for$-$loc loc$)$

$($cond

$[($empty$?$ loc$)$ empty$]$

$[$else

$($cond

$[$cons $($fn$-$for$-$course $($first loc$))($fn$-$for$-$loc $($rest loc$))])]))$

;helper function to filter the an odd number course list

$($define $($filter$-$an$-$odd c$)$

$($filter $($lambda $($x$)($odd$?$ x$)$ c$)))]$

$($cond

$[($and $($course$?$ c$)($equal$?$ LOC$0($course$-$dependents c$)))$

$($filter$-$an$-$odd $($courses$-$w$-$credits c $3))]$

;helper function to filter the an odd number course list

;filter the list of course where the dependents is null, return this list.

$[($and $($course list? $)($map $($lambda $($x$)($equal$?$ LOC$0($last $($course$-$dependents x$))))))$

$(($all$-$course$-$numbers c$))]))]))$

My question: how to extract course$-$dependents value when the input course is a list of course???