Exercise 4.39.  Does the order of the restrictions in the 
multiple-dwelling procedure affect the answer? Does it affect the time 
to find an answer? If you think it matters, demonstrate a faster program 
obtained from the given one by reordering the restrictions. If you think 
it does not matter, argue your case.

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It does not affect the answers, or even the order in which the answers 
are given, but it does affect efficiency.

We can improve it by moving the restrictions that will exclude the 
greatest number of possibilities with the least computational effort 
closest to the top.  For example, comparing (> miller cooper) will be 
fast and will exclude fully half of the possibilities, so we put it 
first.

The distinctness test will be the slowest so we put it last.

(define (multiple-dwelling)
  (let ((baker (amb 1 2 3 4 5))
        (cooper (amb 1 2 3 4 5))
        (fletcher (amb 1 2 3 4 5))
        (miller (amb 1 2 3 4 5))
        (smith (amb 1 2 3 4 5)))
    (require (> miller cooper))
    (require (not (= baker 5)))
    (require (not (= cooper 1)))
    (require (not (= fletcher 5)))
    (require (not (= fletcher 1)))
    (require (not (= (abs (- smith fletcher)) 1)))
    (require (not (= (abs (- fletcher cooper)) 1)))
    (require (distinct? (list baker cooper fletcher miller smith)))
    (list (list 'baker baker)
          (list 'cooper cooper)
          (list 'fletcher fletcher)
          (list 'miller miller)
          (list 'smith smith))))