(define (make-accumulator n)
  (lambda (k)
    (begin
      (set! n (+ n k))
      n)))

; 1 ]=> (define A (make-accumulator 5))
; 
; ;Value: a
; 
; 1 ]=> (A 10)
; 
; ;Value: 15
; 
; 1 ]=> (A 10)
; 
; ;Value: 25