(define (sum-x points)
	(if (null? points) 0
	(+ (caar points) (sum-x (cdr points)))))
;;
(define (sum-y points)
	(if (null? points) 0
	(+ (cadr (car points)) (sum-y (cdr points)))))
;;
(define (average-point points)
	(let ((aver (list (/ (sum-x points) (length points))
		(/ (sum-y points) (length points)))))
	(list (distance-product aver points) aver)))