(define (flip fn)
  (lambda (a b) (fn b a)))

(define (vowel? letter) (member? letter '(a e i o u)))

(define (gertrude wd)
  (se (if (vowel? (first wd)) 'an 'a)
      wd
      'is
      (if (vowel? (first wd)) 'an 'a)
      wd
      'is
	(if (vowel? (first wd)) 'an 'a)
      wd))


(define (sum-square a b)
  (let ((+ *)
        (* +))
    (* (+ a a) (+ b b))))