Guided Practice 4.4 Computing On Lists of Structures

Starting with 04-2-books.rkt (from this week's examples), design the following functions:

;; inventory-total-value : LOB -> Number
;; GIVEN: a LOB
;; RETURNS: the value of all the copies on hand of all the books in the
;; given LOB
;; (inventory-total-value lob1) = 390

(begin-for-test
  (check-equal? 
    (inventory-total-value empty)
    0
    "value of the empty inventory should have been 0")
  (check-equal?
    (inventory-total-value lob1)
    390
    "simple test"))

;; books-out-of-stock : LOB -> LOB
;; GIVEN: a list of books
;; RETURNS: a list of the books that are out of stock in the given LOB
;; Example:
;; (books-out-of-stock lob1) =
;;  (list
;;    (make-book "Shakespeare" "Hamlet" 0 2)
;;    (make-book "Shakespeare" "Macbeth" 0 10))

[ANSWER]