#lang racket
(define (balance lst)
  (define (helper lst counter)
    (cond
      [(empty? lst) counter] ;;base case
      [(list? (first lst)) (helper (rest lst) counter)] ;;unwrap list
      [(eq? (first lst) 'debit) (helper (rest lst) (- counter last))] ;;if debit subtract the amount
      [(eq? (first lst) 'credit) (helper (rest lst) (+ counter last))] ;;if credit add the amount
      [else (helper (rest lst) counter)]
      )
    )
  (helper lst 0)
)

;; Racket
(module+ test
  (require rackunit)
  (check-equal? (balance  (list (list 'credit 5))) 5)
  (check-equal? (balance  (list '(debit 5))) -5)
  (check-equal? (balance '((debit 11) (credit 3))) -8)
  (check-equal? (balance '((debit 3) (credit 5))) 2)
  (check-equal? (balance '((debit 5) (credit 23) (debit 23) (credit 5))) 0))