(define (estimate-integral predicate? x1 x2 y1 y2)
  (define (experiment)
    (predicate? (random-in-range x1 x2) (random-in-range y1 y2)))

  (define (experiment-stream)
    (cons-stream (experiment) (experiment-stream)))

  (define monte-carlo-stream (monte-carlo (experiment-stream) 0 0))

  (define range-square (* (abs (- x2 x1)) (abs (- y2 y1))))

  (stream-map (lambda (x) (* x range-square)) monte-carlo-stream))