(define (MaxSum x y z)

   (+ (cond ((or (> x y) (> x z)) x)

            (else ))

      (cond ((or (> y x) (> y z)) y)

            (else ))

      (cond ((or (> z x) (> z y)) z)

            (else ))))

 (MaxSum   )

 (define (Abs x)

   (cond ((> x ) x)

         ((= x ) )

         ((< x ) (- x))))

 (define (Square x) (* x x))

 (define (Average x y)

   (/ (+ x y) ))

 (define (Improve guess x)

   (Average guess (/ x guess)))

 (define (GoodEnough? guess x)

   (< (Abs (- (Square guess) x)) 0.001))

 (define (SqrtIter guess x)

   (if (GoodEnough? guess x)

       guess

       (SqrtIter (Improve guess x)

                 x)))

 (SqrtIter  )

 (define (last-pair lst)

   (if (<= (length lst) )

       lst

       (last-pair (cdr lst))))

 (define (element-of-set? x set)

   (cond ((null? set) false)

         ((equal? x (car set)) true)

         (else (element-of-set? x (cdr set)))))

 (define (adjoin-set x set)

   (if (element-of-set? x set)

       set

       (cons x set)))

 (define (intersection-set set1 set2)

   (cond ((or (null? set1) (null? set2)) '())

         ((element-of-set? (car set1) set2)

          (cons (car set1)

                (intersection-set (cdr set1) set2)))

         (else (intersection-set (cdr set1) set2))))

 (define (union-set set1 set2)

   (cond ((null? set1) set2)

         ((null? set2) set1)

         ((element-of-set? (car set1) set2)

          (union-set (cdr set1) set2))

         (else (cons (car set1) (union-set (cdr set1) set2)))))

 (define set1 (list    ))

 (define set2 (list    ))

 (element-of-set?  set1)

 (element-of-set?  set1)

 (intersection-set set1 set2)

 (union-set set1 set2)