(define assign-grade
  (lambda (numgrade)
    ; Is numgrade at least 90, inclusive
    (if (> numgrade 89) 'A
        (if (> numgrade 79) 'B
            'C))))


(define grades (list 'f 'd 'c 'b 'a))

(define gimmeagrade
  (lambda (numgrade)
    (list-ref grades numgrade)))