Practice: kiosk totals

(define kiosks '((Nairobi . 12) (Mombasa . 8) (Kisumu . 5)))
(define (sum xs)
  (if (null? xs) 0 (+ (cdar xs) (sum (cdr xs)))))
(define (busiest xs best)
  (cond
   ((null? xs) best)
   ((> (cdar xs) (cdr best)) (busiest (cdr xs) (car xs)))
   (else (busiest (cdr xs) best))))
(print (sum kiosks))
(print (car (busiest (cdr kiosks) (car kiosks))))