#lang sicp

(define (make-monitored f)
  (let ((call-count 0))
    (define (mf arg)
      (cond ((eq? arg 'how-many-calls?) call-count)
            ((eq? arg 'reset-count) (set! call-count 0))
            (else
             (set! call-count (+ call-count 1))
             (f arg))))
    mf))