Use one of the loops on page 313 [HtDP] to revise each of the following three function definitions:

1. The function add-taxes adds 5.5% to each amount in a list of bills.

   (define-struct bill (item amount))
   ;; A Bill is: 
   ;; -- (make-bill Symbol Number)
   
   ;; add-taxes : Listof[Bill] -> Listof[Bill]
   (define (add-taxes lob) 
     (cond
       [(empty? lob) empty]
       [else (cons (make-bill 
                     (bill-item (first lob))
                     (* 1.055 (bill-amount (first lob))))
                   (add-taxes (rest lob)))]))
   
   
   ;; Tests: 
   (equal? (add-taxes (list (make-bill 'apple 1.00))) 
           (list (make-bill 'apple 1.055)))
   
   

   Solution

   (define (add-taxes lob) 
     (local ((define (add b) ;; -- [PT 1 for correct add]
               (make-bill (bill-item b) (* 1.055 (bill-amount b)))))
       (map add lob))) ;; -- [PT 1 for correct choice of loop]
   

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