  Exercise 2.43 :   is having a terrible time doing Exercise 2.42 . His queens procedure seems to work , but it runs extremely slowly . (  never does manage to wait long enough for it to solve even the 6×66×6 case . ) When  asks    for help , she points out that he has interchanged the order of the nested mappings in the flatmap , writing it as

; (flatmap
;  (lambda (new-row)
;    (map (lambda (rest-of-queens)
;           (adjoin-position 
;            new-row k rest-of-queens))
;         (queen-cols (- k 1))))
   ( enumerate - interval 1 board - size ) )
  Explain why this interchange makes the program run slowly . Estimate how long it will take  ’s program to solve the eight - queens puzzle , assuming that the program in Exercise 2.42 solves the puzzle in time TT .

because you call each (queen-cols (- k 1)) board-size times,where is should be 1 time
thus, your bonus time would be board-size T time.
 (flatmap
  (lambda (new-row)
    (map (lambda (rest-of-queens)
           (adjoin-position 
            new-row k rest-of-queens))
         (queen-cols (- k 1))))
  Exercise 2.43 :   is having a terrible time doing Exercise 2.42 . His queens procedure seems to work , but it runs extremely slowly . (  never does manage to wait long enough for it to solve even the 6×66×6 case . ) When  asks    for help , she points out that he has interchanged the order of the nested mappings in the flatmap , writing it as

   ( enumerate - interval 1 board - size ) )
  Explain why this interchange makes the program run slowly . Estimate how long it will take  ’s program to solve the eight - queens puzzle , assuming that the program in Exercise 2.42 solves the puzzle in time TT .

because you call each (queen-cols (- k 1)) board-size times,where is should be 1 time
thus, your bonus time would be board-size T time.