#| BEGIN (Введите свое решение) |#
(define (upper-bound a) 
  (cdr a))

(define (lower-bound b) 
  (car b))

(define (sub-interval x y)
  (make-interval (- (lower-bound x) (upper-bound y))
                 (- (upper-bound x) (lower-bound y))))
#| END |#