(define (make-account balance password)
  (define (withdraw amount)
    (if (>= balance amount)
        (begin (set!  balance (- balance amount))
               balance)
        "Insufficient funds"))
  (define (deposit amount)
    (set! balance (+ balance amount)))

  (define (dispatch m)
    (cond ((eq? m 'withdraw) withdraw)
          ((eq? m 'deposit) deposit)
          (else (error "Unknow request -- MAKE-ACCOUNT"
                       m))))
  (define (validate p op)
    (if (eq? password p)
        (dispatch op)
        (error "error password")))
  
  validate)

(define acc (make-account 100 'psw))