; Return the sum of values in the list of numbers L.
(define (list-sum L)
  (apply + L) )

; Return the average value in the list of numbers L.
(define (mean L)
  (/ (list-sum L) (length L)) )

; Return the largest value in the list L.
(define (list-max L)
  (apply max L) )

; Return the smallest value in the list L.
(define (list-min L)
  (apply min L) )

; Return the range of values in the list of numbers L.
(define (range L)
  (list (list-min L) (list-max L)) )