#| 
   A PR record is
    - (define-struct PR (name exchange profit))
|#

;; project : list[PR] -> list[symbol]
;; return the names of all PR records with profit between 10 and 20 (incl)
(define (project alopr)
  (map PR-name (filter (lambda (a-PR) (<= 10 (PR-profit a-PR) 20)) alopr)))