Problem 3.2: Fibonacci (100 pts)

For this problem, you may use the naturals stream in addition to combine-with defined above. We highly recommend you do not define any other helper functions. Such problems are likely to appear on final exam.

Write fibs, which is a stream where the nth term represents the nth Fibonacci number.

(define fibs
  'YOUR-CODE-HERE
)

;;; Tests
; scm> (slice fibs 0 10)
; (0 1 1 2 3 5 8 13 21 34)