$($define LOC$0$ empty$)$

$($define$-$struct course $($number credits dependents$))$

;;James, pls check below Course instances are correct, $22$ Course number is defined.

$($define C$100($make$-$course $1003$ LOC$0))$

$($define C$210($make$-$course $2104\text{'}($C$110)))$

$($define C$213($make$-$course $2134\text{'}($C$210)))$

$($define C$221($make$-$course $2214\text{'}($C$210)))$

$($define C$313($make$-$course $3133\text{'}($C$213$ C$221)))$

$($define C$317($make$-$course $3173\text{'}($C$213$ C$221)))$

;define list of all course in natural numer

$($define list$-$of$-$course $($list $100210213221313317))$

;define tree$-$list in course numer

$($define tree$-$list $($list C$100$ C$210$ C$213$ C$221$ C$313$ C$317))$

;; helper function to extract course numbers from a single course

$($define $($all$-$course$-$numbers$--$course course$)$

$($list $($course$-$number course$)))$

;; produce a list of all course numbers in the given tree

$($define $($all$-$course$-$numbers tree$)$

$($cond

$[($empty$?$ tree$)$ empty$]$

$[($course$?$ tree$)($all$-$course$-$numbers$--$course tree$)]$

$[($list$?$ tree$)($all$-$course$-$numbers$--$loc tree$)]$

$[$else $($error "Invalid input"$)]))$

;; helper function to extract course numbers from a list of courses

$($define $($all$-$course$-$numbers$--$loc loc$)$

$($apply append $($map all$-$course$-$numbers loc$)))$

$($define $($courses$-$w$-$credits c credits$)$

;; Produce a list of courses and their dependents with credits $>=$ specified credits

$($cond $[(>=($course$-$credits c$)$ credits$)$

$($cons c $($courses$-$w$-$credits$--$loc $($course$-$dependents c$)$ credits$))]$

$[$else

$($courses$-$w$-$credits$--$loc $($course$-$dependents c$)$ credits$)]))$

$($define $($courses$-$w$-$credits$--$loc loc credits$)$

;; Helper function to process a list of courses and their dependents with credits $>=$ specified credits

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

$[$else

$($append $($courses$-$w$-$credits $($first loc$)$ credits$)$

$($courses$-$w$-$credits$--$loc $($rest loc$)$ credits$))]))$

This program snippet doesn't run well for problem $2$ and $3$ below

$($@problem $2)$

;;

;; Design a function that produces the list of all the course numbers in the

;; course's tree including the given course's number.

;;

;; Your @htdf tag and the rest of the design MUST have the definition for

;; the function that takes Course as an argument first. The function that

;; operates on a list must be second. Marks will only be rewarded for

;; solutions that order the design this way.

;;

$($@problem $3)$

;;

;; Design a function that takes two arguments: a Course and a Natural, in that

;; order. It produces the list of courses in the tree that are worth that

;; many credits or more.

;;

;; Your @htdf tag and the rest of the design MUST have the definition for

;; the function that takes Course as an argument first. The function that

;; operates on a list must be second. Marks will only be rewarded for

;; solutions that order the design this way.

;;