(define (cube x) (* x x x))

(define (simpson-iter f a b n k)
  (let* ((h (/ (- b a) n))
	 (y (f (+ a (* k h))))
	 (coeff 
	  (cond ((= k 0) 1)
		((= k n) 1)
		((odd? k) 4)
		((even? k) 2))))
    (+ (* (/ h 3) (* coeff y))
      (if (= k n)
	0
      	(simpson-iter f a b n (+ k 1))))))

(define (simpson-int f a b n)
  (simpson-iter f a b n 0))