Project:
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 ``` ```; interval arithmetic (define (plus x y) (cons (+ (car x) (car y)) (+ (cdr x) (cdr y)))) (define (minus x y) (cons (- (car x) (cdr y)) (- (cdr x) (car y)))) (define (times x y) (cons (min (* (car x) (car y)) (* (car x) (cdr y)) (* (cdr x) (car y)) (* (cdr x) (cdr y))) (max (* (car x) (car y)) (* (car x) (cdr y)) (* (cdr x) (car y)) (* (cdr x) (cdr y))))) (define (divide x y) (if (< (car y) 0 (cdr y)) (error 'divide "divide by zero") (cons (min (/ (car x) (car y)) (/ (car x) (cdr y)) (/ (cdr x) (car y)) (/ (cdr x) (cdr y))) (max (/ (car x) (car y)) (/ (car x) (cdr y)) (/ (cdr x) (car y)) (/ (cdr x) (cdr y)))))) (define (ends->center x) (cons (/ (+ (car x) (cdr x)) 2) (/ (- (cdr x) (car x)) 2))) (define (center->ends x) (cons (- (car x) (cdr x)) (+ (car x) (cdr x)))) (define x (cons 1 2)) (define y (cons 3 4)) (display (plus x y)) (newline) (display (minus x y)) (newline) (display (times x y)) (newline) (display (divide x y)) (newline) (display (ends->center x)) (newline) (display (center->ends (cons 3/2 1/2))) (newline) (display (divide x x)) (newline) ```
 ```1 2 3 4 5 6 7 ``` ```(4 . 6) (-3 . -1) (3 . 8) (1/4 . 2/3) (3/2 . 1/2) (1 . 2) (1/2 . 2) ```